Definition of "No" :
noun: a negative
"His no was loud and clear."
noun: a radioactive transuranic element synthesized by bombarding curium with carbon ions; 7 isotopes are known
adjective: (quantifier) used with either mass nouns or plural count nouns for indicating a complete or almost complete lack or zero quantity of
"We have no bananas."
adverb: used to express refusal or denial or disagreement etc or especially to emphasize a negative statement
"No, you are wrong."
adverb: not in any degree or manner; not at all
"He is no better today."
adverb: referring to the degree to which a certain quality is present
"He was no heavier than a child."