adverb

1. not whether or no
2. not in any degree; not at all no worse
3. nay; not so: the opposite of yes, used to deny, refuse, or disagree

Etymology: ME < OE na < ne a, lit., not ever < IE base *ne, nē, negative particle > Sans ná, Gr ne-, L ne-, Goth & OHG ni, OIr no

interjection

1. it is not so; nay: the opposite of yes
2. it cannot be so: used to express surprise, disbelief, dismay, etc.
3. emphatically not: used to give force to a following negative statement or to introduce a fuller or more specific statement

adjective

Etymology: ME, form of non, none (see none) used only before a consonant < OE nan < ne an, lit., not one (see one)

noun pl. noes or nos

1. an utterance of no; refusal or denial
2. a negative vote, or a person voting in the negative; nay