If you're reading this page, it's a safe bet that you know English grammar. That is, you know how to put words together in a sensible order and add the right endings. Whether or not you've ever opened a grammar book, you know how to produce combinations of sounds and letters that others can understand. After all, English was used for a thousand years before the first grammar books ever appeared.
Knowing about grammar, says David Crystal in The Cambridge Encyclopedia of the English Language (Cambridge University Press, 2003), means "being able to talk about what it is we are able to do when we construct sentences — to describe what the rules are, and what happens when they fail to apply."
In the Cambridge Encyclopedia (one of our Top 10 Reference Works for Writers and Editors), Crystal spends several hundred pages examining all aspects of the English language, including its history and vocabulary, regional and social variations, and the differences between spoken and written English.
But it's the chapters on English grammar that are central to his book, just as grammar itself is central to any study of language. Crystal opens his chapter on "Grammar Mythology" with a list of six reasons to study grammar — reasons worth pausing to think about.
"Because It's There." People are constantly curious about the world in which they live, and wish to understand it and (as with mountains) master it. Grammar is no different from any other domain of knowledge in this respect.
But more than mountains, language is involved with almost everything we do as human beings. We cannot live without language. To understand the linguistic dimension of our existence would be no mean achievement. And grammar is the fundamental organizing principle of language.
Our grammatical ability is extraordinary. It is probably the most creative ability we have. There is no limit to what we can say or write, yet all of this potential is controlled by a finite number of rules. How is this done?
Nonetheless, our language can let us down. We encounter ambiguity, and unintelligible speech or writing. To deal with these problems, we need to put grammar under the microscope, and work out what went wrong. This is especially critical when children are learning to emulate the standards used by educated adult members of their community.
Learning about English grammar provides a basis for learning other languages. Much of the apparatus we need to study English turns out to be of general usefulness. Other languages have clauses, tenses, and adjectives too. And the differences they display will be all the clearer if we have first grasped what is unique to our mother tongue.
After studying grammar, we should be more alert to the strength, flexibility, and variety of our language, and thus be in a better position to use it and to evaluate others' use of it. Whether our own usage in fact improves, as a result, is less predictable. Our awareness must improve, but turning that awareness into better practice — by speaking and writing more effectively — requires an additional set of skills. Even after a course on car mechanics, we can still drive carelessly.
Philosopher Ludwig Wittgenstein said, "Like everything metaphysical the harmony between thought and reality is to be found in the grammar of the language." If that sounds a bit too lofty, we might return to the simpler words of William Langland in his 14th century poem The Vision of Piers Plowman: "Grammer, the ground of al."