What is Definition of Grammar?

Grammar is the structural foundation of our ability to express ourselves. The more we are aware of how it works, the more we can monitor the meaning and effectiveness of the way we and others use language. It can help foster precision, detect ambiguity, and exploit the richness of expression available in English. And it can help everyone--not only teachers of English, but teachers of anything, for all teaching is ultimately a matter of getting to grips with meaning.
(David Crystal, "In Word and Deed," TES Teacher, April 30, 2004)

It is necessary to know grammar, and it is better to write grammatically than not, but it is well to remember that grammar is common speech formulated. Usage is the only test.
(William Somerset Maugham, The Summing Up, 1938)

Hear the word glamour and what comes to mind? Celebrities, most likely--limousines and red carpets, swarms of paparazzi and more money than sense. But, odd as it may sound, glamour comes directly from a decidedly less glamorous word--grammar.
During the Middle Ages, grammar was often used to describe learning in general, including the magical, occult practices popularly associated with the scholars of the day. People in Scotland pronounced grammar as "glam-our," and extended the association to mean magical beauty or enchantment.
In the 19th century, the two versions of the word went their separate ways, so that our study of English grammar today may not be quite as glamorous as it used to be.
But the question remains: what is grammar?

Descriptive Grammar and Prescriptive Grammar

In our Glossary of Grammatical and Rhetorical Terms, you’ll find two definitions of grammar:

1. The systematic study and description of a language.
2. A set of rules and examples dealing with the syntax and word structures of a language, usually intended as an aid to the learning of that language.

Descriptive grammar (definition #1) refers to the structure of a language as it is actually used by speakers and writers. Prescriptive grammar (definition #2) refers to the structure of a language as certain people think it should be used.
Both kinds of grammar are concerned with rules--but in different ways. Specialists in descriptive grammar (called linguists) study the rules or patterns that underlie our use of words, phrases, clauses, and sentences. On the other hand, prescriptive grammarians (such as most editors and teachers) lay out rules about what they believe to be the “correct” or “incorrect” use of language. (See What Is a SNOOT?)

Interfacing With Grammar

To illustrate these different approaches, let's consider the word interface. The descriptive grammarian would note, among other things, that the word is made up of a common prefix (inter-) and a root word (face) and that it’s currently used as both a noun and a verb. The prescriptive grammarian, however, would be more interested in deciding whether or not it is “correct” to use interface as a verb.
Here's how the prescriptive Usage Panel at The American Heritage Dictionary, 4th edition passes judgment on interface:

The Usage Panel has been unable to muster much enthusiasm for the verb. Thirty-seven percent of Panelists accept it when it designates the interaction between people in the sentence The managing editor must interface with a variety of freelance editors and proofreaders. But the percentage drops to 22 when the interaction is between a corporation and the public or between various communities in a city. Many Panelists complain that interface is pretentious and jargony.

Similarly, Bryan A. Garner, author of The Oxford Dictionary of American Usage and Style, dismisses interface as "jargonmongers' talk."
By their nature, all popular style and usage guides are prescriptive, though to varying degrees: some are fairly tolerant of deviations from standard English; others can be downright cranky. The most irascible critics are sometimes called "the Grammar Police."
Though certainly different in their approaches to language, both kinds of grammar--descriptive and prescriptive--are useful to students.

The Value of Studying Grammar

The study of grammar all by itself will not necessarily make you a better writer. But by gaining a clearer understanding of how our language works, you should also gain greater control over the way you shape words into sentences and sentences into paragraphs. In short, studying grammar may help you become a more effective writer.
Descriptive grammarians generally advise us not to be overly concerned with matters of correctness: language, they say, isn't good or bad; it simply is. As the history of the glamorous word grammar demonstrates, the English language is a living system of communication, a continually evolving affair. Within a generation or two, words and phrases come into fashion and fall out again. Over centuries, word endings and entire sentence structures can change or disappear.
Prescriptive grammarians prefer giving practical advice about using language: straightforward rules to help us avoid making errors. The rules may be over-simplified at times, but they are meant to keep us out of trouble--the kind of trouble that may distract or even confuse our readers.
About Grammar & Composition attempts to integrate these two approaches to grammar--or, at the least, present them side by side. For instance, our discussion of the Basic Parts of Speech is primarily descriptive, while our lesson on Correcting Errors in Subject-Verb Agreement is obviously prescriptive.
Thus, the goal of this site is twofold: first, to deepen your understanding of the ways that the English language operates, and second, to serve as a practical guide as you work to become a more confident and effective writer. We look forward to hearing your suggestions on how we might do a better job of meeting both these goals.