A sentence with no subject or verb is an incomplete sentence. That would be a sentence fragment. - - - - - - - - - - - - - A complete sentence requires a subject and that subject's predicate,...
A sentence always provides a complete thought. It has a subject (noun, pronoun) and a predicate (verb, or identity verb), and has end punctuation (period, question mark, or exclamation point)....
The subject of the sentence tells you who it is about. Jenny is nice. Jenny is the subject of this sentence. "What" a sentence is about, however, includes a verb (predicate). Generally you need a...