How would you define English Grammar?
What is Grammar?
Very simply, the rules which govern the use of English.
Is it some set of rules?
Yes, there is an extensive set of rules.
Are these rule static or dynamic?
They are dynamic.
Do these rules change with time and who validates these changes?
Yes, as mentioned, they are dynamic. The only measure of correctness is usage in the broader sense [paraphrased Dwight Bolinger - Linguist]
How would you know that something is grammatical or [a] ungrammatical?
Read this Language Log entry, Anumph. Use CRTL F and type in"zink" to find the right one.
Barbara Scholz and I have taken to using the term correctness conditions for whatever are the actual conditions on your expressions that make them the expressions of your language — and likewise for anyone else's language. If you typically say I ain't got no hammer to explain that you don't have a hammer, then the correctness conditions for your dialect probably include a condition classifying ain't as a negative auxiliary, and a condition specifying that indefinite noun phrases in negated clauses take negative determiners, and a condition specifying that the subject precedes the predicate, and so on. The expressions of your language are the ones that comply with all the correctness conditions that are the relevant ones for you.
Which conditions are the relevant ones for you is an empirical question. Descriptive linguists try to lay out a statement of what the conditions are for particular languages. And it is very important to note that the linguist can go wrong. A linguist can make a mistake in formulating correctness conditions. How would anyone know? Through a back and forth comparison between what the condition statements entail and what patterns are regularly observed in the use of the language by qualified speakers under conditions when they can be taken to be using their language without many errors (e.g., when they are sober, not too tired, not suffering from brain damage, have had a chance to review and edit what they said or wrote, etc.).
Language Log: January 2005 Archives
[Do] Is native speakers' English [is] always grammatical??