not

adv. expressing negation, esp.:
1 (also n't joined to a preceding verb) following an auxiliary verb or be or (in a question) the subject of such a verb (I cannot say; she isn't there; didn't you tell me?; am I not right?; aren't we smart?).
Usage:
Use with other verbs is now archaic (I know not; fear not), except with participles and infinitives (not knowing, I cannot say; we asked them not to come).
2 used elliptically for a negative sentence or verb or phrase (Is she coming? — I hope not; Do you want it? — Certainly not!).
3 used to express the negative of other words (not a single one was left; Are they pleased? - Not they; he is not my cousin, but my nephew).
Phrases and idioms:
not at all (in polite reply to thanks) there is no need for thanks. not but what archaic
1 all the same; nevertheless (I cannot do it; not but what a stronger man might).
2 not such ... or so ... that ... not (not such a fool but what he can see it). not half see HALF. not least with considerable importance, notably. not much see MUCH.
not quite
1 almost (am not quite there).
2 noticeably not (not quite proper). not that (foll. by clause) it is not to be inferred that (if he said so - not that he ever did - he lied). not a thing nothing at all. not very see VERY.
Etymology: ME contr. of NOUGHT