A pseudonym (/ˈsjuːdənɪm/) or alias (/ˈeɪliəs/) is a name that a person or group assumes for a particular purpose, which can differ from their first or true name (orthonym). The term is not used when a new name entirely replaces an individual's own.
Pseudonyms include stage names and user names, ring names, pen names, nicknames, aliases, superhero or villain identities and code names, gamer identifications, and regnal names of emperors, popes, and other monarchs. Historically, they have sometimes taken the form of anagrams, Graecisms, and Latinisations, although there are many other methods of choosing a pseudonym.
Pseudonyms should not be confused with new names that replace old ones and become the individual's full-time name.
Pseudonyms are "part-time" names, used only in certain contexts – to provide a more clear-cut separation between one's private and professional lives, to showcase or enhance a particular persona, or to hide an individual's real identity, as with writers' pen names, graffiti artists' tags, resistance fighters' or terrorists' noms de guerre, and computer hackers' handles. Actors, voice-over artists, musicians, and other performers sometimes use stage names, for example, to better channel a relevant energy, gain a greater sense of security and comfort via privacy, more easily avoid troublesome fans/"stalkers", or to mask their ethnic backgrounds.
A pseudonym may also be used for personal reasons: for example, an individual may prefer to be called or known by a name that differs from their given or legal name, but is not ready to take the numerous steps to get their name legally changed; or an individual may simply feel that the context and content of an exchange offer no reason, legal or otherwise, to provide their given or legal name.
A collective name or collective pseudonym is one shared by two or more persons, for example the co-authors of a work, such as Carolyn Keene, Ellery Queen, Nicolas Bourbaki. or James S. A. Corey.
Distinction from allonyms, ghost writers and pseudepigrapha
A pseudonym is distinct from an allonym, which is the (real) name of another person, assumed by the author of a work of art. This may occur when someone is ghostwriting a book or play, or in parody, or when using a "front" name, such as by screenwriters blacklisted in Hollywood in the 1950s and 1960s. See also pseudepigraph, for falsely attributed authorship.
Legal name change
Sometimes people change their name in such a manner that the new name becomes permanent and is used by all who know the person.
This is not an alias or pseudonym, but in fact a new name.
In many countries, including common law countries, a name change can be ratified by a court and become a person's new legal name.
For example, in the 1960s, black civil rights campaigner Malcolm Little changed his surname to "X", to represent his unknown African ancestral name that had been lost when his ancestors were brought to North America as slaves. He then changed his name again to Malik El-Shabazz when he converted to Islam. Likewise some Jews adopted Hebrew family names upon immigrating to Israel, dropping surnames that had been in their families for generations. The politician David Ben-Gurion, for example, was born David Grün in Poland. He adopted his Hebrew name in 1910, when he published his first article in a Zionist journal in Jerusalem. Many transgender people also choose to adopt a new name, typically around the time of their social transitioning, to resemble their desired gender better than their birth name.
Businesspersons of ethnic minorities in some parts of the world are sometimes advised by an employer to use a pseudonym that is common or acceptable in that area when conducting business, to overcome racial or religious bias.
Criminals may use aliases, fictitious business names, and dummy corporations (corporate shells) to hide their identity, or to impersonate other persons or entities in order to commit fraud. Aliases and fictitious business names used for dummy corporations may become so complex that, in the words of the Washington Post, "getting to the truth requires a walk down a bizarre labyrinth" and multiple government agencies may become involved to uncover the truth.
A pen name, or "nom de plume" (French for "pen name"), is a pseudonym (sometimes a particular form of the real name) adopted by an author (or on the author's behalf by their publishers).
Some female authors used male pen names, in particular in the 19th century, when writing was a male-dominated profession.
The Brontë family used pen names for their early work, so as not to reveal their gender (see below) and so that local residents would not know that the books related to people of the neighbourhood. The Brontës used their neighbours as inspiration for characters in many of their books. Anne Brontë published The Tenant of Wildfell Hall under the name Acton Bell. Charlotte Brontë published Shirley and Jane Eyre under the name Currer Bell. Emily Brontë published Wuthering Heights as Ellis Bell. Another well-known example is Mary Ann Evans, who wrote as George Eliot.
Amandine Aurore Lucile Dupin, a 19th-century French writer, used the pseudonym George Sand. Pseudonyms may also be used due to cultural or organization or political prejudices. There is speculation, for example, that Amelia Bassano Lanier wrote all the Shakespearean sonnets and plays under the name William Shakespeare, primarily because she was a woman who would have been persecuted, prosecuted, or hanged if it were known she had written plays at that time of the 16th to early 17th centuries., and 
A pen name may be used if a writer's real name is likely to be confused with the name of another writer or notable individual, or if the real name is deemed unsuitable.
Authors who write both fiction and non-fiction, or in different genres, may use different pen names to avoid confusing their readers. For example, the romance writer Nora Roberts writes mystery novels under the name J. D. Robb.
Some pen names have been used for long periods, even decades, without the author's true identity being discovered, as with Elena Ferrante and Torsten Krol.
Some pen names are not strictly pseudonyms, as they are simply variants of the authors' actual names.
The authors C. L. Moore and S. E. Hinton were female authors who used the initialled forms of their full names, Moore being Catherine Lucille Moore, writing in the 1930s male-dominated science fiction genre, and Hinton, (author of The Outsiders) Susan Eloise Hinton. Star Trek writer D. C. Fontana (Dorothy Catherine) wrote using her own abbreviated name and under the pen names Michael Richards and J. Michael Bingham. Author V.C. Andrews intended to publish under her given name, Virginia Andrews, but was told that, due to a production error, her first novel was being released under the name of "V.C. Andrews"; later she learned that her publisher had in fact done this deliberately. Joanne Kathleen Rowling published the Harry Potter series as J. K. Rowling. Rowling also published the Cormoran Strike series, a series of detective novels including The Cuckoo's Calling
Winston Churchill wrote as Winston S. Churchill (from his full surname "Spencer-Churchill" which he did not otherwise use) in an attempt to avoid confusion with an American novelist of the same name. The attempt was not wholly successful – the two are still sometimes confused by booksellers.
A pen name may be used specifically to hide the identity of the author, as with exposé books about espionage or crime, or explicit erotic fiction. Some prolific authors adopt a pseudonym to disguise the extent of their published output, e. g. Stephen King writing as Richard Bachman. Co-authors may choose to publish under a collective pseudonym, e. g., P. J. Tracy and Perri O'Shaughnessy. Frederic Dannay and Manfred Lee used the name Ellery Queen as a pen name for their collaborative works and as the name of their main character.
"Why do authors choose pseudonyms?
It is rarely because they actually hope to stay anonymous forever," mused writer and columnist Russell Smith in his review of the Canadian novel Into That Fire by the pseudonymous M. J. Cates. 
A famous case in French literature was Romain Gary. Already a well-known writer, he started publishing books as Émile Ajar to test whether his new books would be well received on their own merits, without the aid of his established reputation. They were: Émile Ajar, like Romain Gary before him, was awarded the prestigious Prix Goncourt by a jury unaware that they were the same person. Similarly, TV actor Ronnie Barker submitted comedy material under the name Gerald Wiley.
A collective pseudonym may represent an entire publishing house, or any contributor to a long-running series, especially with juvenile literature.
Examples include Watty Piper, Victor Appleton, Erin Hunter, and Kamiru M. Xhan.
Another use of a pseudonym in literature is to present a story as being written by the fictional characters in the story.
The series of novels known as A Series Of Unfortunate Events are written by Daniel Handler under the pen name of Lemony Snicket, a character in the series. This applies also to some of the several 18th-century English and American writers who used the name Fidelia.
An anonymity pseudonym or multiple-use name is a name used by many different people to protect anonymity. It is a strategy that has been adopted by many unconnected radical groups and by cultural groups, where the construct of personal identity has been criticised. This has led to the idea of the "open pop star".
Military and paramilitary organizations
In Ancien Régime France, a nom de guerre ("war name") would be adopted by each new recruit (or assigned to them by the captain of their company) as they enlisted in the French army. These pseudonyms had an official character and were the predecessor of identification numbers: soldiers were identified by their first names, their family names, and their noms de guerre (e. g. Jean Amarault dit Lafidélité). These pseudonyms were usually related to the soldier's place of origin (e. g. Jean Deslandes dit Champigny, for a soldier coming from a town named Champigny), or to a particular physical or personal trait (e. g. Antoine Bonnet dit Prettaboire, for a soldier prêt à boire, ready to drink). In 1716, a nom de guerre was mandatory for every soldier; officers did not adopt noms de guerre as they considered them derogatory. In daily life, these aliases could replace the real family name.
Noms de guerre were adopted for security reasons by members of the World War II French resistance and Polish resistance. Such pseudonyms are often adopted by military special-forces soldiers, such as members of the SAS and similar units of resistance fighters, terrorists, and guerrillas. This practice hides their identities and may protect their families from reprisals; it may also be a form of dissociation from domestic life. Some well-known men who adopted noms de guerre include Carlos, for Ilich Ramírez Sánchez; Willy Brandt, Chancellor of West Germany; and Subcomandante Marcos, spokesman of the Zapatista Army of National Liberation (EZLN). During Lehi's underground fight against the British in Mandatory Palestine, the organization's commander Yitzchak Shamir (later Prime Minister of Israel) adopted the nom de guerre "Michael", in honour of Ireland's Michael Collins.
Revolutionaries and resistance leaders, such as Lenin, Trotsky, Golda Meir, Philippe Leclerc de Hauteclocque, and Josip Broz Tito, often adopted their noms de guerre as their proper names after the struggle. George Grivas, the Greek-Cypriot EOKA militant, adopted the nom de guerre Digenis (Διγενής). In the French Foreign Legion, recruits can adopt a pseudonym to break with their past lives. Mercenaries have long used "noms de guerre", sometimes even multiple identities, depending on country, conflict and circumstance. Some of the most familiar noms de guerre today are the kunya used by Islamic mujahideen. These take the form of a teknonym, either literal or figurative.
Individuals using a computer online may adopt or be required to use a form of pseudonym known as a "handle" (a term deriving from CB slang), "user name", "login name", "avatar", or, sometimes, "screen name", "gamertag" "IGN (I n G ame (N ick)Name)" or "nickname". On the Internet, pseudonymous remailers use cryptography that achieves persistent pseudonymity, so that two-way communication can be achieved, and reputations can be established, without linking physical identities to their respective pseudonyms. Aliasing is the use of multiple names for the same data location.
More sophisticated cryptographic systems, such as anonymous digital credentials, enable users to communicate pseudonymously (i. e., by identifying themselves by means of pseudonyms). In well-defined abuse cases, a designated authority may be able to revoke the pseudonyms and reveal the individuals' real identity.
People seeking privacy often use pseudonyms to make appointments and reservations. Those writing to advice columns in newspapers and magazines may use pseudonyms. Steve Wozniak used a pseudonym when attending the University of California, Berkeley after co-founding Apple Computer, because "I knew I wouldn't have time enough to be an A+ student."
Film, theatre, and related activities
Members of a marginalized ethnic or religious group have often adopted stage names, typically changing their surname or entire name to mask their original background.
Stage names are also used to create a more marketable name, as in the case of Creighton Tull Chaney, who adopted the pseudonym Lon Chaney, Jr., a reference to his famous father Lon Chaney, Sr.
Chris Curtis of Deep Purple fame was christened as Christopher Crummey ("crumby" is UK slang for poor quality). In this and similar cases a stage name is adopted simply to avoid an unfortunate pun.
Pseudonyms are also used to comply with the rules of performing arts guilds (Screen Actors Guild (SAG), Writers Guild of America, East (WGA), AFTRA, etc.), which do not allow performers to use an existing name, in order to avoid confusion. For example, these rules required film and television actor Michael Fox to add a middle initial and become Michael J. Fox, to avoid being confused with another actor named Michael Fox. This was also true of author and actress Fannie Flagg, who chose this pseudonym; her real name, Patricia Neal, being the name of another well-known actress; and British actor Stewart Granger, whose real name was James Stewart. The film-making team of Joel and Ethan Coen, for instance, share credit for editing under the alias Roderick Jaynes.
Some stage names are used to conceal a person's identity, such as the pseudonym Alan Smithee, which was used by directors in the Directors Guild of America (DGA) to remove their name from a film they feel was edited or modified beyond their artistic satisfaction. In theatre, the pseudonyms George or Georgina Spelvin, and Walter Plinge are used to hide the identity of a performer, usually when he or she is "doubling" (playing more than one role in the same play).
David Agnew was a name used by the BBC to conceal the identity of a scriptwriter, such as for the Doctor Who serial City of Death, which had three writers, including Douglas Adams, who was at the time of writing the show's Script Editor. In another Doctor Who serial, The Brain of Morbius, writer Terrance Dicks demanded the removal of his name from the credits saying it could go out under a "bland pseudonym". This ended up as Robin Bland.
Musicians and singers can use pseudonyms to allow artists to collaborate with artists on other labels while avoiding the need to gain permission from their own labels, such as the artist Jerry Samuels, who made songs under Napoleon XIV. Rock singer-guitarist George Harrison, for example, played guitar on Cream's song "Badge" using a pseudonym. In classical music, some record companies issued recordings under a nom de disque in the 1950s and 1960s to avoid paying royalties. A number of popular budget LPs of piano music were released under the pseudonym Paul Procopolis. Another example is that Paul McCartney used his fictional name "Bernerd Webb" for Peter and Gordon's song Woman.
Pseudonyms are used as stage names in heavy metal bands, such as Tracii Guns in LA Guns, Axl Rose and Slash in Guns N' Roses, Mick Mars in Mötley Crüe, Dimebag Darrell in Pantera, or C.C. Deville in Poison. Some such names have additional meanings, like that of Brian Hugh Warner, more commonly known as Marilyn Manson: Marilyn coming from Marilyn Monroe and Manson from convicted serial killer Charles Manson. Jacoby Shaddix of Papa Roach went under the name "Coby Dick" during the Infest era. He changed back to his birth name when lovehatetragedy
David Johansen, front man for the hard rock band New York Dolls, recorded and performed pop and lounge music under the pseudonym Buster Poindexter in the late 1980s and early 1990s. The music video for Poindexter's debt single, Hot Hot Hot, opens with a monologue from Johansen where he notes his time with the New York Dolls and explains his desire to create more sophisticated music.
Ross Bagdasarian, Sr., creator of Alvin and the Chipmunks, wrote original songs, arranged, and produced the records under his real name, but performed on them as David Seville. He also wrote songs as Skipper Adams. Danish pop pianist Bent Fabric, whose full name is Bent Fabricius-Bjerre, wrote his biggest instrumental hit "Alley Cat" as Frank Bjorn.
For a time, the musician Prince used an unpronounceable "Love Symbol" as a pseudonym ("Prince" is his actual first name rather than a stage name). He wrote the song "Sugar Walls" for Sheena Easton as "Alexander Nevermind" and "Manic Monday" for The Bangles as "Christopher Tracy". (He also produced albums early in his career as "Jamie Starr").
Many Italian-American singers have used stage names, as their birth names were difficult to pronounce or considered too ethnic for American tastes.
Singers changing their names included Dean Martin (born Dino Paul Crocetti), Connie Francis (born Concetta Franconero), Frankie Valli (born Francesco Castelluccio), Tony Bennett (born Anthony Benedetto), and Lady Gaga (born Stefani Germanotta)
In 2009, the British rock band Feeder briefly changed its name to Renegades so it could play a whole show featuring a set list in which 95 per cent of the songs played were from their forthcoming new album of the same name, with none of their singles included. Front man Grant Nicholas felt that if they played as Feeder, there would be uproar over him not playing any of the singles, so used the pseudonym as a hint. A series of small shows were played in 2010, at 250- to 1,000-capacity venues with the plan not to say who the band really are and just announce the shows as if they were a new band.
In many cases, hip-hop and rap artist prefer to use pseudonyms that represents some variation of their name, personality, or interests.
Examples include Iggy Azalea (her name comes from her dog name, Iggy, and her home street in Mullumbimby, Azalea Street), Ol' Dirty Bastard (who was known under at least six aliases), Diddy (previously known at various times as Puffy, P. Diddy, and Puff Daddy), Ludacris, Flo Rida (his name is a tribute to his home state, Florida), LL Cool J, and Chingy. Black metal artists also adopt pseudonyms, usually symbolizing dark values, such as Nocturno Culto, Gaahl, Abbath, and Silenoz. In punk and hardcore punk, singers and band members often replace real names with tougher-sounding stage names such as Sid Vicious (real name John Simon Ritchie) of the late 1970s band Sex Pistols and "Rat" of the early 1980s band The Varukers and the 2000s re-formation of Discharge. The punk rock band The Ramones had every member take the last name of Ramone.
List of Latinised names
List of pseudonyms
List of pseudonyms used in the American Constitutional debates
List of stage names