Historical grammar is a study of how, say, modern English developed from Middle English, and how that developed from Early and Old English, and how that developed from Germanic, and that developed from what's called Proto-Indo-European, a source system that nobody speaks, so you have to try to reconstruct it.

Nicaragua dealt with the problem of terrorism in exactly the right way. It followed international law and treaty obligations. It collected evidence, brought the evidence to the highest existing tribunal, the International Court of Justice, and received a verdict - which, of course, the U.S. dismissed with contempt.

Descriptive grammar is an attempt to give an account of what the current system is for either a society or an individual, whatever you happen to be studying.

Noam Chomsky Quotes