Depends a bit on your definition of a sentence, but "no" is only an interjection. The sentence lacks a verb and a subject, so some might not consider it complet

Depends a bit on your definition of a sentence, but "no" is only an interjection. The sentence lacks a verb and a subject, so some might not consider it complete. In case of a yes/no question, the rest of the sentence can be thought elided, which would make it complete. It is, however, perfectly clear.