In linguistics, syntax  is the set of rules, principles, and processes that govern the structure of sentences (sentence structure) in a given language, usually including word order. The term syntax is also used to refer to the study of such principles and processes. The goal of many syntacticians is to discover the syntactic rules common to all languages.
The word syntax comes from Ancient Greek: "coordination", which consists of syn, "together", and táxis, "an ordering".
One basic description of a language's syntax is the sequence in which the subject (S), verb (V), and object (O) usually appear in sentences. Over 85% of languages usually place the subject first, either in the sequence SVO or the sequence SOV. The other possible sequences are VSO, VOS, OVS, and OSV, the last three of which are rare. In most generative theories of syntax, these surface differences arise from a more complex clausal phrase structure, and each order may be compatible with multiple derivations.
The Adhy?y? of Pini (c. 4th century BC in Ancient India), is often cited as an example of a premodern work that approaches the sophistication of a modern syntactic theory (as works on grammar were written long before modern syntax came about). In the West, the school of thought that came to be known as "traditional grammar" began with the work of Dionysius Thrax.
For centuries, a framework known as grammaire générale (first expounded in 1660 by Antoine Arnauld in a book of the same title) dominated work in syntax: as its basic premise the assumption that language is a direct reflection of thought processes and therefore there is a single, most natural way to express a thought.
However, in the 19th century, with the development of historical-comparative linguistics, linguists began to realize the sheer diversity of human language and to question fundamental assumptions about the relationship between language and logic. It became apparent that there was no such thing as the most natural way to express a thought, and therefore logic could no longer be relied upon as a basis for studying the structure of language.
The Port-Royal grammar modeled the study of syntax upon that of logic. (Indeed, large parts of the Port-Royal Logic were copied or adapted from the Grammaire générale.) Syntactic categories were identified with logical ones, and all sentences were analyzed in terms of "subject - copula - predicate". Initially, this view was adopted even by the early comparative linguists such as Franz Bopp.
The central role of syntax within theoretical linguistics became clear only in the 20th century, which could reasonably be called the "century of syntactic theory" as far as linguistics is concerned. (For a detailed and critical survey of the history of syntax in the last two centuries, see the monumental work by Giorgio Graffi (2001).)
There are a number of theoretical approaches to the discipline of syntax. One school of thought, founded in the works of Derek Bickerton, sees syntax as a branch of biology, since it conceives of syntax as the study of linguistic knowledge as embodied in the human mind. Other linguists (e.g., Gerald Gazdar) take a more Platonistic view, since they regard syntax to be the study of an abstract formal system. Yet others (e.g., Joseph Greenberg) consider syntax a taxonomical device to reach broad generalizations across languages.
Syntacticians have attempted to explain the causes of word-order variation within individual languages and cross-linguistically. Much of such work has been done within frameworks of generative grammar which assumes that the core of syntax depends on a genetic structure which is common to all mankind. Typological research of the languages of the world has however found few absolute universals, leading some to conclude that none of syntax has to be directly genetic.
Alternative explanations have been sought in language processing. It is suggested that the brain finds it easier to parse syntactic patterns which are either right or left branching, but not mixed. The most widely held approach is the performance-grammar correspondence hypothesis by John A. Hawkins who suggests that language is a non-innate adaptation to innate cognitive mechanisms. Cross-linguistic tendencies are considered as being based on language users' preference for grammars that are organized efficiently, and on their avoidance of word orderings which cause processing difficulty. Some languages however exhibit regular inefficient patterning. These include the VO languages Chinese, with the adpositional phrase before the verb, and Finnish which has postpositions; but there are few other profoundly exceptional languages.
Dependency grammar is an approach to sentence structure where syntactic units are arranged according to the dependency relation, as opposed to the constituency relation of phrase structure grammars. Dependencies are directed links between words. The (finite) verb is seen as the root of all clause structure and all the other words in the clause are either directly or indirectly dependent on this root. Some prominent dependency-based theories of syntax are:
Lucien Tesnière (1893-1954) is widely seen as the father of modern dependency-based theories of syntax and grammar. He argued vehemently against the binary division of the clause into subject and predicate that is associated with the grammars of his day (S -> NP VP) and which remains at the core of most phrase structure grammars. In the place of this division, he positioned the verb as the root of all clause structure.
Categorial grammar is an approach that attributes the syntactic structure not to rules of grammar, but to the properties of the syntactic categories themselves. For example, rather than asserting that sentences are constructed by a rule that combines a noun phrase (NP) and a verb phrase (VP) (e.g., the phrase structure rule S -> NP VP), in categorial grammar, such principles are embedded in the category of the head word itself. So the syntactic category for an intransitive verb is a complex formula representing the fact that the verb acts as a function word requiring an NP as an input and produces a sentence level structure as an output. This complex category is notated as (NP\S) instead of V. NP\S is read as "a category that searches to the left (indicated by \) for an NP (the element on the left) and outputs a sentence (the element on the right)." The category of transitive verb is defined as an element that requires two NPs (its subject and its direct object) to form a sentence. This is notated as (NP/(NP\S)) which means "a category that searches to the right (indicated by /) for an NP (the object), and generates a function (equivalent to the VP) which is (NP\S), which in turn represents a function that searches to the left for an NP and produces a sentence."
Functionalist models of grammar study the form-function interaction by performing a structural and a functional analysis.
The hypothesis of generative grammar is that language is a biological structure. The difference between structural-functional and generative models is that, in generative grammar, the object is placed into the verb phrase. Generative grammar is meant to be used to describe all human language and to predict whether any given utterance in a hypothetical language would sound correct to a speaker of that language (versus constructions which no human language would use). This approach to language was pioneered by Noam Chomsky. Most generative theories (although not all of them) assume that syntax is based upon the constituent structure of sentences. Generative grammars are among the theories that focus primarily on the form of a sentence, rather than its communicative function.
Among the many generative theories of linguistics, the Chomskyan theories are:
Other theories that find their origin in the generative paradigm are:
The Cognitive Linguistics framework stems from generative grammar, but adheres to evolutionary rather than Chomskyan linguistics. Cognitive models often recognise the generative assumption that the object belongs to the verb phrase. Cognitive frameworks include:
[The Adhy?y?] is a highly precise and thorough description of the structure of Sanskrit somewhat resembling modern generative grammar...[it] remained the most advanced linguistic analysis of any kind until the twentieth century.
Nous avons emprunté...ce que nous avons dit...d'un petit Livre...sous le titre de Grammaire générale.