Definitions of no:

• noun:   a negative

  Example: "His no was loud and clear"

• noun:   a radioactive transuranic element synthesized by bombarding curium with carbon ions; 7 isotopes are known
• adverb:   used to express refusal or denial or disagreement etc or especially to emphasize a negative statement

  Example: "No, you are wrong"

• adverb:   not in any degree or manner; not at all

  Example: "He is no better today"

• adverb:   referring to the degree to which a certain quality is present

  Example: "He was no heavier than a child"

• name:  A surname (very rare: popularity rank in the U.S.: #25272)