Meaning

1. not (used alone to negate a verb; now chiefly with only a few particular verbs: see usage notes)
2. not, no (used before a verb, with a coordinating negative element usually following; see Usage Notes, below)
3. Used in a subordinate clause before a subjunctive verb (especially when the main verb expresses doubt or fear), to provide extra overtones of doubt or uncertainty (but not negating its verb); the so-called "pleonastic" or "expletive" ne.
4. In comparative clauses usually translated with the positive sense of the subsequent negative