Not is an English word. It functions as the negative dependent polarity particle in English. It can also be used as a conjunction.
In traditional grammar, not is usually analysed as an adverb. However, its syntax is not similar to prototypical adverbs, and is probably best analysed separately.
It can be fused with auxiliary verbs to form negative contractions.
Not is one of the most common words in English.
It is negative n- as an independent morpheme.