So you think you know grammar? All well and good, but which type of grammar do you know?
One basic distinction worth making is that between descriptive grammar and prescriptive grammar (also called usage). Both are concerned with rules--but in different ways. Specialists in descriptive grammar examine the rules or patterns that underlie our use of words, phrases, clauses, and sentences. In contrast, prescriptive grammarians (such as most editors and teachers) try to enforce rules about what they believe to be the correct uses of language.
But that's just the beginning. Consider these ten varieties of grammar--and take your pick.
The analysis and comparison of the grammatical structures of related languages. Contemporary work in comparative grammar is concerned with "a faculty of language that provides an explanatory basis for how a human being can acquire a first language . . .. In this way, the theory of grammar is a theory of human language and hence establishes the relationship among all languages." (R. Freidin, Principles and Parameters in Comparative Grammar. MIT Press, 1991)
The rules determining the structure and interpretation of sentences that speakers accept as belonging to the language. "Simply put, a generative grammar is a theory of competence: a model of the psychological system of unconscious knowledge that underlies a speaker's ability to produce and interpret utterances in a language." (F. Parker and K. Riley, Linguistics for Non-Linguists. Allyn and Bacon, 1994)
The generative grammar stored in the brain that allows a speaker to produce language that other speakers can understand. "All humans are born with the capacity for constructing a Mental Grammar, given linguistic experience; this capacity for language is called the Language Faculty (Chomsky, 1965). A grammar formulated by a linguist is an idealized description of this Mental Grammar." (P. W. Culicover and A. Nowak, Dynamical Grammar: Foundations of Syntax II. Oxford Univ. Press, 2003)
Grammatical analysis and instruction designed for second-language students. "Pedagogical grammar is a slippery concept. The term is commonly used to denote (1) pedagogical process--the explicit treatment of elements of the target language systems as (part of) language teaching methodology; (2) pedagogical content--reference sources of one kind or another that present information about the target language system; and (3) combinations of process and content." (D. Little, "Words and Their Properties: Arguments for a Lexical Approach to Pedagogical Grammar." Perspectives on Pedagogical Grammar, ed. by T. Odlin. Cambridge Univ. Press, 1994)
A description of the syntax of English as it is actually used by speakers in dialogues. "[P]erformance grammar . . . centers attention on language production; it is my belief that the problem of production must be dealt with before problems of reception and comprehension can properly be investigated." (John Carroll, "Promoting Language Skills." Perspectives on School Learning: Selected Writings of John B. Carroll, ed. by L. W. Anderson. Erlbaum, 1985)
A description of the grammar of a language, with explanations of the principles governing the construction of words, phrases, clauses, and sentences. Examples of contemporary reference grammars in English include A Comprehensive Grammar of the English Language, by Randolph Quirk et al. (1985), the Longman Grammar of Spoken and Written English (1999), and The Cambridge Grammar of the English Language (2002).
The study of the essential components of any human language. "Theoretical grammar or syntax is concerned with making completely explicit the formalisms of grammar, and in providing scientific arguments or explanations in favour of one account of grammar rather than another, in terms of a general theory of human language." (A. Renouf and A. Kehoe, The Changing Face of Corpus Linguistics. Rodopi, 2003)
The collection of prescriptive rules and concepts about the structure of the language. "We say that traditional grammar is prescriptive because it focuses on the distinction between what some people do with language and what they ought to do with it, according to a pre-established standard. . . . The chief goal of traditional grammar, therefore, is perpetuating a historical model of what supposedly constitutes proper language." (J. D. Williams, The Teacher's Grammar Book. Routledge, 2005)
A theory of grammar that accounts for the constructions of a language by linguistic transformations and phrase structures. "In transformational grammar, the term 'rule' is used not for a precept set down by an external authority but for a principle that is unconsciously yet regularly followed in the production and interpretation of sentences. A rule is a direction for forming a sentence or a part of a sentence, which has been internalized by the native speaker." (D. Bornstein, An Introduction to Transformational Grammar. Univ. Press of America, 1984)
The system of categories, operations, and principles shared by all human languages and considered to be innate. "Taken together, the linguistic principles of Universal Grammar constitute a theory of the organization of the initial state of the mind/brain of the language learner--that is, a theory of the human faculty for language." (S. Crain and R. Thornton, Investigations in Universal Grammar. MIT Press, 2000)
If ten varieties of grammar aren't enough for you, rest assured that new grammars are emerging all the time. There's word grammar, for instance. And relational grammar. Not to mention cognitive grammar, construction grammar, lexical functional grammar, head-driven phrase structure grammar . . . and many more.