A prison, also known as a correctional facility, detention center (US English), jail (US and Australia), gaol (dated) (British English), penitentiary (sometimes used in American English) or remand centre is a facility in which inmates are forcibly confined and denied a variety of freedoms under the authority of the state. Prisons are most commonly used within a criminal justice system: people charged with crimes may be imprisoned until they are brought to trial; those pleading or being found guilty of crimes at trial may be sentenced to a specified period of imprisonment. Besides their use for punishing crimes, jails and prisons are frequently used by authoritarian regimes against perceived opponents.
The term prison or penitentiary is often used to describe institutions that incarcerate people for longer periods of time, such as many years, while the term jail is more often used to describe institutions focused on confining people for shorter periods of time (e.g. for shorter sentences or while waiting for trial / sentencing). Prisons often have facilities that are more designed with long term confinement in mind in comparison to jails. 
Prisons can be used as a tool of political repression to punish what are deemed political crimes, often without trial or other legal due process; this use is illegal under most forms of international law governing fair administration of justice. In times of war, prisoners of war or detainees may be detained in military prisons or prisoner of war camps, and large groups of civilians might be imprisoned in internment camps.
Common slang terms for prison include: "The Stir", "The Pokey", "The Slammer", "The Joint", "The Calaboose", "The Hoosegow", "The Big House", and "Up The River" (a possible reference to Sing Sing).
The use of prisons can be traced back to the rise of the state as a form of social organization. Corresponding with the advent of the state was the development of written language, which enabled the creation of formalized legal codes as official guidelines for society. The best known of these early legal codes is the Code of Hammurabi, written in Babylon around 1750 BC. The penalties for violations of the laws in Hammurabi's Code were almost exclusively centered on the concept of lex talionis ("the law of retaliation"), whereby people were punished as a form of vengeance, often by the victims themselves. This notion of punishment as vengeance or retaliation can also be found in many other legal codes from early civilizations, including the ancient Sumerian codes, the Indian Manama Dharma Astra, the Hermes Trismegistus of Egypt, and the Israelite Mosaic Law.
Some Ancient Greek philosophers, such as Plato, began to develop ideas of using punishment to reform offenders instead of simply using it as retribution. Imprisonment as a penalty was used initially for those who could not afford to pay their fines. Eventually, since impoverished Athenians could not pay their fines, leading to indefinite periods of imprisonment, time limits were set instead.  The prison in Ancient Athens was known as the desmoterion ("place of chains"). 
The Romans were among the first to use prisons as a form of punishment, rather than simply for detention. A variety of existing structures were used to house prisoners, such as metal cages, basements of public buildings, and quarries. One of the most notable Roman prisons was the Mamertine Prison, established around 640 B.C. by Ancus Marcius. The Mamertine Prison was located within a sewer system beneath ancient Rome and contained a large network of dungeons where prisoners were held in squalid conditions, contaminated with human waste. Forced labor on public works projects was also a common form of punishment. In many cases, citizens were sentenced to slavery, often in ergastula (a primitive form of prison where unruly slaves were chained to workbenches and performed hard labor).
Middle Ages to the 17th century
During the Middle Ages in Europe, castles, fortresses, and the basements of public buildings were often used as makeshift prisons. The possession of the right and the capability to imprison citizens, however, granted an air of legitimacy to officials at all levels of government, from kings to regional courts to city councils; and the ability to have someone imprisoned or killed served as a signifier of who in society possessed power or authority over others. Another common punishment was sentencing people to galley slavery, which involved chaining prisoners together in the bottoms of ships and forcing them to row on naval or merchant vessels.
However, the concept of the modern prison largely remained unknown until the early 19th-century. Punishment usually consisted of physical forms of punishment, including capital punishment, mutilation, flagellation (whipping), branding, and non-physical punishments, such as public shaming rituals (like the stocks).  From the Middle Ages up to the 16th and 17th centuries in Europe, imprisonment was rarely used as a punishment in its own right, and prisons were mainly to hold those awaiting trial and convicts awaiting punishment.
However, an important innovation at the time was the Bridewell House of Corrections, located at Bridewell Palace in London, which resulted in the building of other houses of correction. These houses held mostly petty offenders, vagrants, and the disorderly local poor. In these facilities, inmates were given jobs, and through prison labor they were taught how to work for a living. By the end of the 17th century, houses of correction were absorbed into local prison facilities under the control of the local justice of the peace. 
From the late 17th century and during the 18th century, popular resistance to public execution and torture became more widespread both in Europe and in the United States. Particularly under the Bloody Code, with few sentencing alternatives, imposition of the death penalty for petty crimes, such as theft, was proving increasingly unpopular with the public; many jurors were refusing to convict defendants of petty crimes when they knew the defendants would be sentenced to death. Rulers began looking for means to punish and control their subjects in a way that did not cause people to associate them with spectacles of tyrannical and sadistic violence. They developed systems of mass incarceration, often with hard labor, as a solution.   The prison reform movement that arose at this time was heavily influenced by two somewhat contradictory philosophies. The first was based in Enlightenment ideas of utilitarianism and rationalism, and suggested that prisons should simply be used as a more effective substitute for public corporal punishments such as whipping, hanging, etc. This theory, referred to as deterrence, claims that the primary purpose of prisons is to be so harsh and terrifying that they deter people from committing crimes out of fear of going to prison. The second theory, which saw prisons as a form of rehabilitation or moral reform, was based on religious ideas that equated crime with sin, and saw prisons as a place to instruct prisoners in Christian morality, obedience and proper behavior. These later reformers believed that prisons could be constructed as humane institutions of moral instruction, and that prisoners' behavior could be "corrected" so that when they were released, they would be model members of society. 
Transportation, prison ships and penal colonies
England used penal transportation of convicted criminals (and others generally young and poor) for a term of indentured servitude within the general population of British America between the 1610s and 1776. The Transportation Act 1717 made this option available for lesser crimes, or offered it by discretion as a longer-term alternative to the death penalty, which could theoretically be imposed for the growing number of offenses. The substantial expansion of transportation was the first major innovation in eighteenth-century British penal practice.  Transportation to America was abruptly suspended by the Criminal Law Act 1776 (16 Geo. 3 c.43)   with the start of the American Rebellion. While sentencing to transportation continued, the act instituted a punishment policy of hard labour instead. The suspension of transport also prompted the use of prisons for punishment and the initial start of a prison building program.  Britain would resume transportation to specifically planned penal colonies in Australia between 1788 and 1868. 
Gaols at the time were run as business ventures, and contained both felons and debtors; the latter were often housed with their wives and younger children. The gaolers made their money by charging the inmates for food, drink, and other services, and the system was generally corruptible. One reform of the seventeenth century was the establishment of the London Bridewell as a house of correction for women and children. It was the first facility to make any medical services available to prisoners.
With the widely used alternative of penal transportation halted in the 1770s, the immediate need for additional penal accommodations emerged. Given the undeveloped institutional facilities, old sailing vessels, termed hulks, were the most readily available and expandable choice to be used as places of temporary confinement. While conditions on these ships were generally appalling, their use and the labor thus provided set a precedent which persuaded many people that mass incarceration and labour were viable methods of crime prevention and punishment. The turn of the 19th century would see the first movement toward Prison reform, and by the 1810s, the first state prisons and correctional facilities were built, thereby inaugurating the modern prison facilities available today.
France also sent criminals to overseas penal colonies, including Louisiana, in the early 18th century. Penal colonies in French Guiana operated until 1952, such as the notable Devil's Island (Île du Diable ). Katorga prisons were harsh work camps established in the 17th century in Russia, in remote underpopulated areas of Siberia and the Russian Far East, that had few towns or food sources. Siberia quickly gained its fearful connotation of punishment.
Prison reform movement
John Howard was one of the most notable early prison reformers.  After having visited several hundred prisons across England and Europe, in his capacity as high sheriff of Bedfordshire, he published The State of the Prisons in 1777.  He was particularly appalled to discover prisoners who had been acquitted but were still confined because they couldn't pay the gaoler's fees. He proposed wide-ranging reforms to the system, including the housing of each prisoner in a separate cell; the requirements that staff should be professional and paid by the government, that outside inspection of prisons should be imposed, and that prisoners should be provided with a healthy diet and reasonable living conditions. The prison reform charity, the Howard League for Penal Reform, was established in 1866 by his admirers. 
Following Howard's agitation, the Penitentiary Act was passed in 1779. This introduced solitary confinement, religious instruction, a labor regime, and proposed two state penitentiaries (one for men and one for women). However, these were never built due to disagreements in the committee and pressures from wars with France, and gaols remained a local responsibility. But other measures passed in the next few years provided magistrates with the powers to implement many of these reforms, and eventually, in 1815, gaol fees were abolished.
Quakers were prominent in campaigning against and publicizing the dire state of the prisons at the time. Elizabeth Fry documented the conditions that prevailed at Newgate prison, where the ladies' section was overcrowded with women and children, some of whom had not even received a trial. The inmates did their own cooking and washing in the small cells in which they slept on straw. In 1816, Fry was able to found a prison school for the children who were imprisoned with their parents. She also began a system of supervision and required the women to sew and to read the Bible. In 1817, she helped found the Association for the Reformation of the Female Prisoners in Newgate.
Development of the modern prison
The theory of the modern prison system was born in London, influenced by the utilitarianism of Jeremy Bentham. Bentham's panopticon introduced the principle of observation and control that underpins the design of the modern prison. The notion of prisoners being incarcerated as part of their punishment and not simply as a holding state until trial or hanging, was at the time revolutionary. His views influenced the establishment of the first prisons used as criminal rehabilitation centers. At a time when the implementation of capital punishment for a variety of relatively trivial offences was on the decline, the notion of incarceration as a form of punishment and correction held great appeal to reform-minded thinkers and politicians.
In the first half of the 19th century, capital punishment came to be regarded as inappropriate for many crimes that it had previously been carried out for, and by the mid-19th century, imprisonment had replaced the death penalty for the most serious offenses except for murder. 
The first state prison in England was the Millbank Prison, established in 1816 with a capacity for just under 1000 inmates. By 1824, 54 prisons had adopted the disciplinary system advocated by the SIPD. By the 1840s, penal transportation to Australia and the use of hulks was on the decline, and the Surveyor-General of convict prisons, Joshua Jebb, set an ambitious program of prison building in the country, with one large prison opening per year. Pentonville prison opened in 1842, beginning a trend of ever increasing incarceration rates and the use of prison as the primary form of crime punishment. Robert Peel's Gaols Act of 1823 introduced regular visits to prisoners by chaplains, provided for the payment of gaolers and prohibited the use of irons and manacles.
In 1786, the state of Pennsylvania passed a law which mandated that all convicts who had not been sentenced to death would be placed in penal servitude to do public works projects such as building roads, forts, and mines. Besides the economic benefits of providing a free source of hard labor, the proponents of the new penal code also thought that this would deter criminal activity by making a conspicuous public example of consequences of breaking the law. However, what actually ended up happening was frequent spectacles of disorderly conduct by the convict work crews, and the generation of sympathetic feelings from the citizens who witnessed the mistreatment of the convicts. The laws quickly drew criticism from a humanitarian perspective (as cruel, exploitative and degrading) and from a utilitarian perspective (as failing to deter crime and delegitimizing the state in the eyes of the public). Reformers such as Benjamin Rush came up with a solution that would enable the continued used of forced labor, while keeping disorderly conduct and abuse out of the eyes of the public. They suggested that prisoners be sent to secluded "houses of repentance" where they would be subjected (out of the view of the public) to "bodily pain, labour, watchfulness, solitude, and silence ... joined with cleanliness and a simple diet".  
Pennsylvania soon put this theory into practice, and turned its old jail at Walnut Street in Philadelphia into a state prison, in 1790. This prison was modeled on what became known as the "Pennsylvania system" (or "separate system"), and placed all prisoners into solitary cells with nothing other than religious literature, and forced them to be completely silent to reflect on their wrongs.  New York soon built the Newgate state prison in Greenwich Village, which was modeled on the Pennsylvania system,  and other states followed.
But by 1820 faith in the efficacy of legal reform had declined as statutory changes had no discernible effect on the level of crime and the prisons, where prisoners shared large rooms and booty including alcohol, had become riotous and prone to escapes. In response, New York developed the Auburn system in which prisoners were confined in separate cells and prohibited from talking when eating and working together, implementing it at Auburn State Prison and Sing Sing at Ossining. The aim of this was rehabilitative: the reformers talked about the penitentiary serving as a model for the family and the school and almost all the states adopted the plan (though Pennsylvania went even further in separating prisoners). The system's fame spread and visitors to the U.S. to see the prisons included de Tocqueville who wrote Democracy in America as a result of his visit. 
The use of prisons in Continental Europe was never as popular as it became in the English-speaking world, although state prison systems were largely in place by the end of the 19th century in most European countries. After the unification of Italy in 1861, the government reformed the repressive and arbitrary prison system they inherited, and modernized and secularized criminal punishment by emphasizing discipline and deterrence. Italy developed an advanced penology under the leadership of Cesare Lombroso (1835–1909).
Another prominent prison reformer who made important contributions was Alexander Paterson who advocated for the necessity of humanising and socialising methods within the prison system in Great Britain and America.
Prisons are normally surrounded by fencing, walls, earthworks, geographical features, or other barriers to prevent escape. Multiple barriers, concertina wire, electrified fencing, secured and defensible main gates, armed guard towers, security lighting, motion sensors, dogs and roving patrols may all also be present depending on the level of security. 
Remotely controlled doors, CCTV monitoring, alarms, cages, restraints, nonlethal and lethal weapons, riot-control gear and physical segregation of units and prisoners may all also be present within a prison to monitor and control the movement and activity of prisoners within the facility. 
Modern prison designs have increasingly sought to restrict and control the movement of prisoners throughout the facility and also to allow a smaller prison staff to monitor prisoners directly; often using a decentralized "podular" layout.   (In comparison, 19th-century prisons had large landings and cell blocks which permitted only intermittent observation of prisoners.) Smaller, separate and self-contained housing units known as "pods" or "modules" are designed to hold 16 to 50 prisoners and are arranged around exercise yards or support facilities in a decentralized "campus" pattern. A small number of prison officers, sometimes a single officer, supervise each pod. The pods contain tiers of cells arranged around a central control station or desk from which a single officer can monitor all the cells and the entire pod, control cell doors and communicate with the rest of the prison.
Pods may be designed for high-security "indirect supervision", in which officers in segregated and sealed control booths monitor smaller numbers of prisoners confined to their cells. An alternative is "direct supervision", in which officers work within the pod and directly interact with and supervise prisoners, who may spend the day outside their cells in a central "dayroom" on the floor of the pod. Movement in or out of the pod to and from exercise yards, work assignments or medical appointments can be restricted to individual pods at designated times and is generally centrally controlled. Goods and services, such as meals, laundry, commissary, educational materials, religious services and medical care can increasingly be brought to individual pods or cells as well. 
Inmate security classifications
Generally, when an inmate arrives at a prison, they go through a security classification screening and risk assessment that determines where they will be placed within the prison system. Classifications are assigned by assessing the prisoner's personal history and criminal record, and through subjective determinations made by intake personnel (which include mental health workers, counselors, prison unit managers, and others). This process will have a major impact on the prisoner's experience, determining their security level, educational and work programs, mental health status (e.g. will they be placed in a mental health unit), and many other factors. This sorting of prisoners is one of the fundamental techniques through which the prison administration maintains control over the inmate population, and creates an orderly and secure prison environment.    At most prisons, prisoners are made to wear prison uniform.
The levels of security within a prison system are categorized differently around the world, but tend to follow a distinct pattern. At one end of the spectrum are the most secure facilities ("maximum security"), which typically hold prisoners that are considered dangerous, disruptive or likely to try to escape. Furthermore, in recent times, supermax prisons have been created where the custody level goes beyond maximum security for people such as terrorists or political prisoners deemed a threat to national security, and inmates from other prisons who have a history of violent or other disruptive behavior in prison or are suspected of gang affiliation. These inmates have individual cells and are kept in lockdown, often for more than 23 hours per day. Meals are served through "chuck holes" in the cell door, and each inmate is allotted one hour of outdoor exercise per day, alone. They are normally permitted no contact with other inmates and are under constant surveillance via closed-circuit television cameras. 
On the other end are "minimum security" prisons which are most often used to house those for whom more stringent security is deemed unnecessary. For example, while white-collar crime rarely results in incarceration, when it does offenders are almost always sent to minimum-security prisons due to them having committed nonviolent crimes.  Lower-security prisons are often designed with less restrictive features, confining prisoners at night in smaller locked dormitories or even cottage or cabin-like housing while permitting them free movement around the grounds to work or activities during the day. Some countries (such as Britain) also have "open" prisons where prisoners are allowed home-leave or part-time employment outside of the prison. Suomenlinna Island facility in Finland is an example of one such "open" correctional facility. The prison has been open since 1971 and, as of September 2013, the facility's 95 male prisoners leave the prison grounds on a daily basis to work in the corresponding township or commute to the mainland for either work or study. Prisoners can rent flat-screen televisions, sound systems, and mini-refrigerators with the prison-labor wages that they can earn—wages range between 4.10 and 7.30€ per hour. With electronic monitoring, prisoners are also allowed to visit their families in Helsinki and eat together with the prison staff. Prisoners in Scandinavian facilities are permitted to wear their own clothes. 
Modern prisons often hold hundreds or thousands of inmates, and must have facilities onsite to meet most of their needs, including dietary, health, fitness, education, religious practices, entertainment, and many others. Conditions in prisons vary widely around the world, and the types of facilities within prisons depend on many intersecting factors including funding, legal requirements, and cultural beliefs/practices. Nevertheless, in addition to the cell blocks that contain the prisoners, also there are certain auxiliary facilities that are common in prisons throughout the world.
Kitchen and dining
Prisons generally have to provide food for a large number of individuals, and thus are generally equipped with a large institutional kitchen. There are many security considerations, however, that are unique to the prison dining environment. For instance, cutlery equipment must be very carefully monitored and accounted for at all times, and the layout of prison kitchens must be designed in a way that allows staff to observe activity of the kitchen staff (who are usually prisoners). The quality of kitchen equipment varies from prison to prison, depending on when the prison was constructed, and the level of funding available to procure new equipment. Prisoners are often served food in a large cafeteria with rows of tables and benches that are securely attached to the floor. However, inmates that are locked in control units, or prisons that are on "lockdown" (where prisoners are made to remain in their cells all day) have trays of food brought to their cells.  It is said that prison food of many developed countries is adequate to maintain health and dieting. 
Prisons in wealthy, industrialized nations provide medical care for most of their inmates. Additionally, prison medical staff play a major role in monitoring, organizing, and controlling the prison population through the use of psychiatric evaluations and interventions (psychiatric drugs, isolation in mental health units, etc.). Prison populations are largely from poor minority communities that experience greater rates of chronic illness, substance abuse, and mental illness than the general population. This leads to a high demand for medical services, and in countries such as the US that don't provide free healthcare, prison is often the first place that people are able to receive medical treatment (which they couldn't afford outside).   
Prison medical facilities include primary care, mental health services, dental care, substance abuse treatment, and other forms of specialized care, depending on the needs of the inmate population. Health care services in many prisons have long been criticized as inadequate, underfunded, and understaffed, and many prisoners have experienced abuse and mistreatment at the hands of prison medical staff who are entrusted with their care.   
Despite the fact that studies reveal more than 50% of those incarcerated are likely to suffer from at least one mental illness or condition, the verdict of "not guilty by reason of insanity" is exceedingly rare according to a 2014 Scientific American article. In the United States, a million people who are incarcerated suffer from mental illness without any assistance or treatment for their condition and the tendency of a convicted criminal to reoffend, known as the rate of recidivism, is unusually high for those with the most serious disorders.  Analysis of data in 2000 from several forensic hospitals in California, New York and Oregon found that with treatment the rate of recidivism was "much lower" than untreated mentally ill offenders.  Treatment works to lower crime among those who are mentally ill, but public support is often shaded by stigmas. Without public support, funding is restricted and the cycle of recidivism that feeds the U.S. prison system is perpetuated.  The issue of health care for prisoners with mental illness is not a moral issue, it is a psychological issue, and if treatment were readily available, crime would decrease as would the rate of recidivism among those who are mentally ill who are essentially trapped in a prison system that offers little to no relief. 
Library and educational facilities
Some prisons provide educational programs for inmates that can include basic literacy, secondary education, or even college education. Prisoners seek education for a variety of reasons, including the development of skills for after release, personal enrichment and curiosity, finding something to fill their time, or trying to please prison staff (which can often secure early release for good behavior). However, the educational needs of prisoners often come into conflict with the security concerns of prison staff and with a public that wants to be "tough on crime" (and thus supports denying prisoners access to education). Whatever their reasons for participating in educational programs, prison populations tend to have very low literacy rates and lack of basic mathematical skills, and many have not completed secondary education. This lack of basic education severely limits their employment opportunities outside of prison, leading to high rates of recidivism, and research has shown that prison education can play a significant role in helping prisoners reorient their lives and become successful after reentry.  
Many prisons also provide a library where prisoners can check out books, or do legal research for their cases.  Often these libraries are very small, consisting of a few shelves of books. In some countries, such as the United States, drastic budget cuts have resulted in many prison libraries being shut down. Meanwhile, many nations that have historically lacked prison libraries are starting to develop them.  Prison libraries can dramatically improve the quality of life for prisoners, who have large amounts of empty time on their hands that can be occupied with reading. This time spent reading has a variety of benefits including improved literacy, ability to understand rules and regulations (leading to improved behavior), ability to read books that encourage self-reflection and analysis of one's emotional state, consciousness of important real-world events, and education that can lead to successful re-entry into society after release.  
Recreation and fitness
Many prisons provide limited recreational and fitness facilities for prisoners. The provision of these services is controversial, with certain elements of society claiming that prisons are being "soft" on inmates, and others claiming that it is cruel and dehumanizing to confine people for years without any recreational opportunities. The tension between these two opinions, coupled with lack of funding, leads to a large variety of different recreational procedures at different prisons. Prison administrators, however, generally find the provision of recreational opportunities to be useful at maintaining order in the prisons, because it keeps prisoners occupied and provides leverage to gain compliance (by depriving prisoners of recreation as punishment). Examples of common facilities/programs that are available in some prisons are: gyms and weightlifting rooms, arts and crafts, games (such as cards, chess, or bingo), television sets, and sports teams.  Additionally, many prisons have an outdoor recreation area, commonly referred to as an "exercise yard".
Most prisoners are part of the "general population" of the prison, members of which are generally able to socialize with each other in common areas of the prison.  A control unit or segregation unit (also called a "block" or "isolation cell") is a highly secure area of the prison, where inmates are placed in solitary confinement to isolate them from the general population.  Other prisoners that are often segregated from the general population include those who are in protective custody, or who are on suicide watch, and those whose behavior presents a threat to other prisoners.
In addition to the above facilities, others that are common include prison factories and workshops, visiting areas, mail rooms, telephone and computer rooms, a prison store (often called a "canteen") where prisoners can purchase goods, or a death row where prisoners who have been sentenced to death await execution.
Youth detention facilities
Prisons for juveniles are known by a variety of names, including "youth detention facilities", "juvenile detention centers", and "reformatories". The idea of separately treating youthful and adult offenders is a relatively modern idea. The earliest known use of the term "juvenile delinquency" was in London in 1816, from where it quickly spread to the United States. The first juvenile correctional institution in the United States opened in 1825 in New York City. By 1917, juvenile courts had been established in all but 3 states. It was estimated that in 2011 more than 95,000 juveniles were locked up in prisons and jails in the United States (the largest youth prisoner population in the world).  Besides prisons, many other types of residential placement exist within juvenile justice systems, including youth homes, community-based programs, training schools and boot camps.
Like adult facilities, youth detention centers in some countries are experiencing overcrowding due to large increases in incarceration rates of young offenders. Crowding can create extremely dangerous environments in juvenile detention centers and juvenile correctional facilities. Overcrowding may also lead to the decrease in availability to provide the youth with much needed and promised programs and services while they are in the facility. Many times the administration is not prepared to handle the large number of residents and therefore the facilities can become unstable and create instability in simple logistics. 
In addition to overcrowding, juvenile prisons are questioned for their overall effectiveness in rehabilitating youth. Many critics note high juvenile recidivism rates, and the fact that the most of the youths that are incarcerated are those from lower socio-economic classes (who often suffer from broken families, lack of educational/job opportunities, and violence in their communities). 
The majority of women incarcerated have experienced abuse before prison, and while they are incarcerated they may suffer from post-traumatic stress disorder.  Sexual offenses against women prisoners can include rape, assault, and groping during pat frisks. Male correctional officials often violate women prisoners’ privacy by watching them undress, shower, and go to the bathroom. Research suggests that, “women with histories of abuse are more likely to accept sexual misconduct from prison staff because they are already conditioned to respond to coercion and threats by acquiescing to protect themselves from further violence”.  “In federal women’s correction facilities, 70% of guards are male,”  reinforcing female inmates’ powerlessness.
Most inmates are women of color from low socioeconomic backgrounds and therefore suffer from both chronic diseases that are common in minorities (such as diabetes, heart disease, and hypertension) and health problems that may result from living in poverty (such as malnutrition, etc.). Incarcerated women suffer disproportionately from HIV/AIDS, infectious disease, reproductive issues, and chronic diseases. Within the American prison system, HIV became more prevalent among women than among men. According to the U.S. Department of Justice, from 1991 to 1998 the number of women prisoners with HIV increased by 69%, while the equivalent figure among male prisoners decreased by 22% during the same time period. The New York State Department of Health stated in 1999 that women entering New York state prisons had twice as high of an HIV rate as men entering New York state prisons. At the end of the year 2000 women in U.S. state prison systems had a 60% higher likelihood of carrying HIV than men in American state prison systems. 
The needs of mothers during pregnancy and childbirth often conflict with the demands of the prison system. “In 2007, the Bureau of Justice Statistics stated that, on average, 5% of women who enter into state prisons are pregnant and in jails 6% of women are pregnant”.  Very few of these women receive prenatal care, which can be very detrimental to both the mother and child, especially when coupled with inmates’ histories of inadequate health care as well as sexual, physical and substance abuse. Most of these pregnancies are deemed as high risk. Additionally, a lack of maternity clothes and resources to deal with premature births, false labors, and miscarriages pose serious challenges to prisoners. Furthermore, incarcerated women are a source of free labor for private companies. It is recorded that if women decline to work, then their medicinal needs are not fulfilled.  This becomes a major issue for pregnant women who may not physically be able to work but are in dire need of medical care. Most pregnant women are shackled on grounds of security in labor and delivery.  The Eighth Circuit Court of Appeals established that is unconstitutional in 2009, and prohibited restraint of women during labor. 
Military prisons and prisoner-of-war camps
Prisons have formed parts of military systems since the French Revolution. France set up its system in 1796. They were modernized in 1852 and since their existence, are used variously to house prisoners of war, unlawful combatants, those whose freedom is deemed a national security risk by military or civilian authorities, and members of the military found guilty of a serious crime. Military prisons in the United States have also been converted to civilian prisons, to include Alcatraz Island. Alcatraz was formerly a military prison for soldiers during the American Civil War.
In the American Revolution, British prisoners held by the U.S. were assigned to local farmers as laborers. The British kept American sailors in broken down ship hulks with high death rates.
In the Napoleonic wars, the broken down hulks were still in use for naval prisoners. One French surgeon recalled his captivity in Spain, where scurvy, diarrhea, dysentery, and typhus abounded, and prisoners died by the thousands:
- ""These great trunks of ships were immense coffins, in which living men were consigned to a slow death.... [In the hot weather we had] black army bread full of gritty particles, biscuit full of maggots, salt meat that was already decomposing, rancid lard, spoiled cod, [and] stale rice, peas, and beans." 
In the American Civil War, at first prisoners of war were released, after they promised not to fight again unless formally exchanged. When the Confederacy refused to exchange black prisoners the system broke down, and each side built large-scale POW camps. Conditions in terms of housing, food and medical care were bad in the Confederacy, and the Union retaliated by imposing harsh conditions. 
By 1900 the legal framework of the Geneva and Hague Convention provided considerable protection. In the First World War, millions of prisoners were held on both sides, with no major atrocities. Officers received privileged treatment. There was an increase in the use of forced labor throughout Europe. Food and medical treatment were generally comparable to what active duty soldiers received, and housing was much better than front-line conditions. 
Political prisons and administrative detention
Political prisoners are people who have been imprisoned because of their political beliefs, activities and affiliations. There is much debate about who qualifies as a "political prisoner". The category of "political prisoner" is often contested, and many regimes that incarcerate political prisoners often claim that they are merely "criminals". Others who are sometimes classified as "political prisoners" include prisoners who were politicized in prison, and are subsequently punished for their involvement with political causes.   
Many countries maintain or have in the past had a system of prisons specifically intended for political prisoners. In some countries, dissidents can be detained, tortured, executed, and/or "disappeared" without trial. This can happen either legally, or extralegally (sometimes by falsely accusing people and fabricating evidence against them). 
Administrative detention is a classification of prisons or detention centers where people are held without trial.
Some psychiatric facilities have characteristics of prisons, particularly when confining patients who have committed a crime and are considered dangerous.  In addition, many prisons have psychiatric units dedicated to housing offenders diagnosed with a wide variety of mental disorders. The United States government refers to psychiatric prisons as " Federal Medical Centers (FMC) ".
Some jurisdictions refer to the prison population (total or per-prison) as the prison muster. 
As of 2010 it was estimated that at least 10.1 million people were imprisoned worldwide. 
As of 2012 the United States of America had the world's largest prison population, with over 2.3 million people in American prisons or jails—up from 744,000 in 1985—making 1 in every 100 American adults a prisoner. That same year it was also reported that the United States government spent an estimated US$37 billion to maintain prisons.  The cost of these prisons was then estimated at US$74 billion per year.  
As of 2009 California's 158,000 inmates were detained in prisons that were designed to hold 84,000—almost 14,000 of these inmates were sleeping in very tight spaces, or in hallways, or on floors. People are also being incarcerated at an increasing rate and new prisons cannot be built fast enough. As of 2009 China had a prison population of about 1.6 million,  while the prison population of India was 332,112. 
A mid-November 2013 news report announced that four prisons in Sweden closed during the year due to a significant drop in the number of inmates. The head of Sweden's prison and probation services characterised the decrease in the number of Swedish prisoners as "out-of-the-ordinary", with prison numbers in Sweden falling by around 1% a year since 2004. Prisons closed in the towns of Åby, Håja, Båtshagen, and Kristianstad. 
Economics of the prison industry
In the United States alone, more than $74 billion per year is spent on prisons, with over 800,000 people employed in the prison industry.  As the prison population grows, revenues increase for a variety of small and large businesses that construct facilities, and provide equipment (security systems, furniture, clothing), and services (transportation, communications, healthcare, food) for prisons. These parties have a strong interest in the expansion of the prison system since their development and prosperity directly depends on the number of inmates. 
The prison industry also includes private businesses that benefit from the exploitation of the prison labor.   Some scholars, using the term prison-industrial complex, have argued that the trend of "hiring out prisoners" is a continuation of the slavery tradition, pointing out that the Thirteenth Amendment to the United States Constitution freed slaves but allowed forced labor for people convicted of crimes.  Prisons are very attractive to employers, because prisoners can be made to perform a great array of jobs, under conditions that most free laborers wouldn't accept (and would be illegal outside of prisons): sub-minimum wage payments, no insurance, no collective bargaining, lack of alternative options, etc. Prison labor can soon deprive the free labor of jobs in a number of sectors, since the organized labor turns out to be uncompetitive compared to the prison counterpart. 
Social effects of mass incarceration
Mass incarceration has a powerful negative influence on communities (particularly poor communities), creating broken families, economic disenfranchisement, and increases in criminal activity. In many poor neighborhoods in the U.S., as many as one fifth of the adult men are in prison at any given time. When they are released, they are unable to find work, earn less money when they do find work, and experience a wide range of medical and psychological issues that make it harder for them to integrate back into society. Because of the lack of opportunities for former prisoners, rates of recidivism are very high; according to the Bureau of Justice Statistics, within three years of release, 67.8 percent of released prisoners are rearrested and within five years, 76.6 percent are rearrested.  This dynamic affects not only the individuals who are incarcerated, but the families and communities around them, who have to pick up the burden while they are away (e.g. one parent who has to work and raise their children alone, because the other parent is imprisoned or teachers who have to deal with disciplinary problems from children who are acting out due to broken families).    Furthermore, spending billions of dollars every year on prisons often results in funding shortages for social welfare programs like schools, food aid, and healthcare, which address the poverty that fuels much of the criminal activity in many poor communities.  
As a result of the ineffectiveness of prisons at preventing crime, the high costs of maintaining them, and the detrimental socio-economic effects of mass incarceration, many nations (e.g. Sweden,  Germany, and the Netherlands ) have been working towards policies of large-scale decarceration, addressing crime and violence with alternative strategies such as fines, community service, and restorative justice processes. In addition to moving towards a more wholistic style of punishment, Nordic Countries in particular are focusing their efforts on prevention. In Sweden local police now work with county government to target at-risk youths. Swedish children from dysfunctional homes are provided more education and after-school activities to try and keep them out of trouble. In addition, police in Nordic countries are less likely to arrest youth for minor violations of the law. If a teenager steals food from a grocery store, they are often given community service time. 
Theories of punishment and criminality
A variety of justifications and explanations are put forth for why people are imprisoned by the state. The most common of these are:
- Rehabilitation: Theories of rehabilitation claim that the experience of being imprisoned will cause people to change their lives in a way that will make them productive and law-abiding members of society once they are released. However, this is not supported by empirical evidence, and in practice prisons tend to be ineffective at improving the lives of most prisoners.  As Morris and Rothman (1995) point out, "It's hard to train for freedom in a cage." While the view of prisons as centers of rehabilitation was popular during the early development of the modern prison system, it is not widely held anymore, and has mostly been replaced by theories of deterrence, incapacitation, and retribution. 
- Deterrence: Theories of deterrence claim that by sentencing criminals to extremely harsh penalties, other people who might be considering criminal activities will be so terrified of the consequences that they will choose not to commit crimes out of fear. In reality, most studies show that high incarceration rates either increase crime, have no noticeable effect, or only decrease it by a very small amount.  Prisons act as training grounds for criminal activity, form criminal social networks, expose prisoners to further abuse (both from staff and other prisoners), foster anti-social sentiments towards society (law enforcement and corrections personnel in particular), fragment communities, and leave prisoners with criminal records that make it difficult to find legal employment after release. All of these things can result in a higher likelihood of reoffending upon release.  
- Incapacitation: Justifications based on incapacitation claim that while prisoners are incarcerated, they will be unable to commit crimes, thus keeping communities safer. Critics point out that this is based on a false distinction between "inside" and "outside", and that the prisoners will simply continue to victimize people inside of the prison (and in the community once they are released), and that the harm done by these actions has real impacts on the society outside of the prison walls. 
- Retribution: Theories of retribution seek to exact revenge upon criminals by harming them in exchange for harms caused to their victims. These theories do not necessarily focus on whether or not a particular punishment benefits the community, but are more concerned with ensuring that the punishment causes a sufficient level of misery for the prisoner, in proportion to the perceived seriousness of their crime. These theories are based upon a belief that some kind of moral balance will be achieved by "paying back" the prisoner for the wrongs they have committed. 
Conditional sentences are sentences that are served outside of the prison walls and in the community with some sort of restrictions or conditions placed on the offender, in an effort to reduce prison populations. The requirements or conditions may include mandatory programs such as a drug or alcohol treatment seminars, curfews, house arrest, or electronic monitoring. Most offenders who receive conditional sentences are low risk and are usually serving time for impaired driving where no death occurred. When an offender receives a conditional sentence of home confinement in comparison to incarceration, the offender is still able to see family members, maintain a normal job, and attend school. This is a huge advantage to conditional sentencing, since offenders are not completely cut off from the external world. Although the offender is not locked away in a prison cell, the offender is still expected to stay at home during certain times of the day or night. In order to verify that offenders are abiding by the restrictions placed on them, electronic monitoring is often used. The development of GPS, which allows law enforcement agencies to know the exact location of the offender by the use of satellites, has increased the effectiveness of offenders serving home confinement sentences drastically. Offenders can now easily be identified and tracked down through the use of GPS allowing law enforcement officers to quickly move in to make an arrest when an offender is in breach of their conditions.
The prison abolition movement seeks to reduce or eliminate prisons and the prison system, and replace them with more humane and effective systems. It is distinct from prison reform,  which is the attempt to improve conditions inside prisons; however, relying on prisons less can significantly improve their conditions by eliminating overcrowding.  Abolitionists criticize the focus on "crime" as violations of laws that are arbitrarily defined by those in power—especially when these lawmakers are seen as oppressive and corrupt.  Abolitionists see most anti-social acts (violence, theft, etc.) as the result of social problems (e.g. poverty, racism, sexism) that cannot be dealt with by simply punishing individuals, and instead require systemic changes to address the underlying structural causes.  
Restorative justice  is an approach to justice that focuses on the needs of the victims and the offenders, as well as the involved community, instead of focusing on satisfying abstract legal principles or punishing offenders (such as imprisoning them). Victims take an active role in the process, while offenders are encouraged to take responsibility for their actions, "to repair the harm they've done—by apologizing, returning stolen money, or community service".   
- Note that in Britain a 'detention centre' is a military detention facility, not a prison
- In American English,prisonandjailare often distinguished from one another. See below for further information.
- From the Old Frenchprisoun
- Other commonly used terms areremand centreanddetention centre. In some legal systems some of these terms have distinct meanings. For instance, in the United States, "jail" and "prison" refer to separate levels of incarceration; generally speaking, jails are county or city-administrated institutions which house both inmates awaiting trial on the local level and convicted misdemeanants serving a term of one year or less, while prisons are state or federal facilities housing convicted felons serving a term of more than one year.
- For a more detailed look at the English "transportation" system, and the transition from penal colonies to prisons, see Hostettler, John (2009).. Waterside Press. p. 157. ISBN 9781906534790.
- For an in-depth treatment of Bentham's panopticon, see Semple, Janet (1993).. Oxford University Press. ISBN 978-0-19-159081-8.
- But some authors have pointed out that many historical treatments overemphasize Howard's work, and that there were many other individuals (including local prison administrators) that also played a significant role in the development of modern prisons. See DeLacy, Margaret (1986). "The Eighteenth Century Gaol".. Manchester University Press. ISBN 9780719013416.
- There were several reasons that early prison reformers sought to move punishment out of the view of the public, by placing prisons away from population centers and restricting access to the inside of prison facilities. For a detailed history of the ideological origins of these practices of concealment and exclusion, see: Kann, Mark E. (2005). "Concealing Punishment".. NYU Press. ISBN 978-0-8147-4783-4.
- For a broad overview of the technologies used in prison security, see: Latessa, Edward J. (1996). "Technology". In McShane, Marilyn D. & Williams, Frank P.. Taylor & Francis. ISBN 9781135582708.
- For a history of the development of prison libraries, see Coyle, William (1987).. Greenwood Publishing Group. ISBN 9780313247699. and Wiegand, Wayne A. & Davis, Donald G., eds. (1994). "Prison libraries".. Routledge. ISBN 9780824057879.
- For a detailed discussion of the sometimes blurred line between "criminals" and "political prisoners", see: Wachsmann, Nikolaus (2004).. Yale University Press. ISBN 9780300102505.
- For a detailed look at the demographics of the U.S. prison population, see Simon, Rita & de Waal, Christiaan (2009). "United States".. Rowman & Littlefield. ISBN 9780739140246.
- Also frequently referred to as "reformation" or "corrections"
- For instance, prior to the U.S. Civil War, slaves who escaped captivity were "breaking the law". People who resisted the Nazi government in Germany or the Apartheid government in South Africa were also seen as "criminals" and punished by the judicial system. But while of these people committed crimes, few today would argue that "justice" was served by punishing them.
- Sometimes called "reparative justice" (See Weitekamp, Elmar (1993). (PDF). European Journal on Criminal Policy and Research. 1 (1): 70–93. doi:. )