In linguistics, grammar (from Ancient Greek γραμματική) is the set of structural rules governing the composition of clauses, phrases and words in a natural language. The term refers also to the study of such rules and this field includes phonology, morphology and syntax, often complemented by phonetics, semantics and pragmatics.

Fluent speakers of a language variety or lect have a set of internalized rules for using that form of speech. This rule set constitutes the lect's grammar.^[1] The vast majority of the information in the grammar is – at least in the case of one's native language – acquired not by conscious study or instruction but by hearing other speakers. Much of this work is done during early childhood; learning a language later in life usually involves a greater degree of explicit instruction.^[2] Thus, grammar is the cognitive information underlying language use.

The term "grammar" can also be used to describe the rules that govern the linguistic behavior of a group of speakers.

For example, the term "English grammar" might have several meanings.

It may refer to the whole of English grammar; that is, to the grammars of all the speakers of the language, in which case the term encompasses a great deal of variation.^[3] Alternatively, it may refer only to what is common to the grammars of all or of the vast majority of English speakers (such as subject–verb–object word order in simple declarative sentences). It may also refer to the rules of a particular, relatively well-defined variety of English (such as standard English for a region).

A description, study or analysis of such rules may also be referred to as a grammar.

A reference book describing the grammar of a language is called a "reference grammar" or simply "a grammar" (see History of English grammars). A fully explicit grammar that exhaustively describes the grammatical constructions of a particular speech variety is called a descriptive grammar. This kind of linguistic description contrasts with linguistic prescription, an attempt to actively discourage or suppress some grammatical constructions, while codifying and promoting others, either in an absolute sense or in reference to a standard variety. Preposition stranding occurs widely in Germanic languages, has a long history in English and is generally considered standard usage. John Dryden (13 April 1668 – January 1688) objected to it (without explanation), leading other English speakers to avoid the construction and discourage its use.^[4][5]

Outside linguistics, the term grammar is often used in a rather different sense. It may be used more broadly to include rules of spelling and punctuation, which linguists would not typically consider to form part of grammar but rather as a part of orthography, the conventions used for writing a language. It may also be used more narrowly to refer to a set of prescriptive norms only, excluding those aspects of a language's grammar that are not subject to variation or debate on their normative acceptability. Jeremy Butterfield claimed that, for non-linguists, "Grammar is often a generic way of referring to any aspect of English that people object to."^[6]

The word grammar is derived from Greek γραμματικὴ τέχνη (grammatikē technē), which means "art of letters", from γράμμα (gramma), "letter", itself from γράφειν (graphein), "to draw, to write".^[7] The same Greek root also appears in graphics, grapheme, and photograph.

The first systematic grammar, of Sanskrit, originated in Iron Age India, with Yaska (6th century BC), Pāṇini (6-5th century BC^[8]) and his commentators Pingala (c. 200 BC), Katyayana, and Patanjali (2nd century BC). Tolkāppiyam, the earliest Tamil grammar, is mostly dated to before the 5th century AD. The Babylonians also made some early attempts at language description.^[9]

In the West, grammar emerged as a discipline in Hellenism from the 3rd century BC forward with authors like Rhyanus and Aristarchus of Samothrace. The oldest known grammar handbook is the Art of Grammar (Τέχνη Γραμματική), a succinct guide to speaking and writing clearly and effectively, written by the ancient Greek scholar Dionysius Thrax (c. 170–c. 90 BC), a student of Aristarchus of Samothrace who established a school on the Greek island of Rhodes.^[10] Dionysius Thrax's grammar book remained the primary grammar textbook for Greek schoolboys until as late as the twelfth century AD.^[10] The Romans based their grammatical writings on it and its basic format remains the basis for grammar guides in many languages even today.^[10] Latin grammar developed by following Greek models from the 1st century BC, due to the work of authors such as Orbilius Pupillus, Remmius Palaemon, Marcus Valerius Probus, Verrius Flaccus, and Aemilius Asper.

A grammar of Irish originated in the 7th century with the Auraicept na n-Éces. Arabic grammar emerged with Abu al-Aswad al-Du'ali in the 7th century. The first treatises on Hebrew grammar appeared in the High Middle Ages, in the context of Mishnah (exegesis of the Hebrew Bible). The Karaite tradition originated in Abbasid Baghdad. The Diqduq (10th century) is one of the earliest grammatical commentaries on the Hebrew Bible.^[11] Ibn Barun in the 12th century compares the Hebrew language with Arabic in the Islamic grammatical tradition.^[12]

Belonging to the trivium of the seven liberal arts, grammar was taught as a core discipline throughout the Middle Ages, following the influence of authors from Late Antiquity, such as Priscian. Treatment of vernaculars began gradually during the High Middle Ages, with isolated works such as the First Grammatical Treatise, but became influential only in the Renaissance and Baroque periods. In 1486, Antonio de Nebrija published Las introduciones Latinas contrapuesto el romance al Latin, and the first Spanish grammar, Gramática de la lengua castellana, in 1492. During the 16th-century Italian Renaissance, the Questione della lingua was the discussion on the status and ideal form of the Italian language, initiated by Dante's de vulgari eloquentia (Pietro Bembo, Prose della volgar lingua Venice 1525). The first grammar of Slovene was written in 1583 by Adam Bohorič.

Grammars of non-European languages began to be compiled for the purposes of evangelization and Bible translation from the 16th century onward, such as Grammatica o Arte de la Lengua General de los Indios de los Reynos del Perú (1560), and a Quechua grammar by Fray Domingo de Santo Tomás.

From the latter part of the 18th century, grammar came to be understood as a subfield of the emerging discipline of modern linguistics.

The Deutsche Grammatik of the Jacob Grimm was first published in the 1810s. The Comparative Grammar of Franz Bopp, the starting point of modern comparative linguistics, came out in 1833.

Frameworks of grammar, which attempt to give a precise scientific theory of the syntax rules of grammar and their function, have been developed in theoretical linguistics. Most mainstream frameworks are based on the conception of an innate "universal grammar", an idea developed by Noam Chomsky. The most prominent theories are:

Parse trees are commonly (but not always) used by such frameworks to depict their rules. There are various additional notation schemes for some grammars:

Grammars evolve through usage and also due to separations of the human population.

With the advent of written representations, formal rules about language usage tend to appear also. Formal grammars are codifications of usage that are developed by repeated documentation over time, and by observation as well. As the rules become established and developed, the prescriptive concept of grammatical correctness can arise. This often creates a discrepancy between contemporary usage and that which has been accepted, over time, as being standard or "correct". Linguists tend to view prescriptive grammars as having little justification beyond their authors' aesthetic tastes, although style guides may give useful advice about standard language employment, based on descriptions of usage in contemporary writings of the same language. Linguistic prescriptions also form part of the explanation for variation in speech, particularly variation in the speech of an individual speaker (an explanation, for example, for why some people say "I didn't do nothing", some say "I didn't do anything", and some say one or the other depending on social context).

The formal study of grammar is an important part of education for children from a young age through advanced learning, though the rules taught in schools are not a "grammar" in the sense most linguists use the term, particularly as they are prescriptive in intent rather than descriptive.

Constructed languages (also called planned languages or conlangs) are more common in the modern day than they used to be, although still extremely uncommon compared to natural languages. Many have been designed to aid human communication (for example, naturalistic Interlingua, schematic Esperanto, and the highly logic-compatible artificial language Lojban). Each of these languages has its own grammar.

Syntax refers to the linguistic structure above the word level (e.g. how sentences are formed) – though without taking into account intonation, which is the domain of phonology. Morphology, by contrast, refers to structure at and below the word level (e.g. how compound words are formed), but above the level of individual sounds, which, like intonation, are in the domain of phonology.^[13] No clear line can be drawn, however, between syntax and morphology. Analytic languages use syntax to convey information that is encoded via inflection in synthetic languages. In other words, word order is not significant and morphology is highly significant in a purely synthetic language, whereas morphology is not significant and syntax is highly significant in an analytic language. Chinese and Afrikaans, for example, are highly analytic, and meaning is therefore very context-dependent. (Both do have some inflections, and have had more in the past; thus, they are becoming even less synthetic and more "purely" analytic over time.) Latin, which is highly synthetic, uses affixes and inflections to convey the same information that Chinese does with syntax. Because Latin words are quite (though not completely) self-contained, an intelligible Latin sentence can be made from elements that are placed in a largely arbitrary order. Latin has a complex affixation and simple syntax, while Chinese has the opposite.

Prescriptive grammar is taught in primary and secondary school. The term "grammar school" historically refers to a school (attached to a cathedral or monastery) teaching Latin grammar to future priests and monks. In its earliest form, "grammar school" referred to a school that taught students to read, scan, interpret, and declaim Greek and Latin poets (including Homer, Virgil, Euripides, and others). These should not be confused with the related, albeit distinct, modern British grammar schools.

A standard language is a particular dialect of a language that is promoted above other dialects in writing, education, and broadly speaking in the public sphere; it contrasts with vernacular dialects, which may be the objects of study in academic, descriptive linguistics but which are rarely taught prescriptively. The standardized "first language" taught in primary education may be subject to political controversy, because it may sometimes establish a standard defining nationality or ethnicity.

Recently, efforts have begun to update grammar instruction in primary and secondary education. The primary focus has been to prevent the use of outdated prescriptive rules in favor of laying down norms based on prior descriptive research and to change perceptions about relative "correctness" of prescribed standard forms in comparison to non-standard dialects.

The pre-eminence of Parisian French has reigned largely unchallenged throughout the history of modern French literature. Standard Italian is not based on the speech of the capital, Rome, but on the speech of Florence because of the influence Florentines had on early Italian literature. Similarly, standard Spanish is not based on the speech of Madrid, but on that of educated speakers from more northerly areas like Castile and León (e.g. see Gramática de la lengua castellana). In Argentina and Uruguay the Spanish standard is based on the local dialects of Buenos Aires and Montevideo (Rioplatense Spanish). Portuguese has, for now, two official standards, respectively Brazilian Portuguese and European Portuguese.

The Serbian variant of Serbo-Croatian is divided in a similar way; Serbia and the Republika Srpska of Bosnia and Herzegovina use their own distinct normative subvarieties, with differences in yat reflexes. The existence and codification of a distinct Montenegrin standard is a matter of controversy, some treat Montenegrin as a separate standard lect and some think it should be considered another form of Serbian.

Norwegian has two standards, Bokmål and Nynorsk, the choice between which is subject to controversy: Each Norwegian municipality can declare one of the two its official language, or it can remain "language neutral". Nynorsk is endorsed by a minority of 27 percent of the municipalities. The main language used in primary schools normally follows the official language of its municipality and is decided by referendum within the local school district. Standard German emerged from the standardized chancellery use of High German in the 16th and 17th centuries. Until about 1800, it was almost entirely a written language, but now it is so widely spoken that most of the former German dialects are nearly extinct.

Standard Chinese has official status as the standard spoken form of the Chinese language in the People's Republic of China (PRC), the Republic of China (ROC) and the Republic of Singapore. Pronunciation of Standard Chinese is based on the local accent of Mandarin Chinese from Luanping, Chengde in Hebei Province near Beijing, while grammar and syntax are based on modern vernacular written Chinese. Modern Standard Arabic is directly based on Classical Arabic, the language of the Qur'an. The Hindustani language has two standards, Hindi and Urdu.

In the United States, the Society for the Promotion of Good Grammar designated 4 March as National Grammar Day in 2008.^[14]