Any statement which does not meet the definition of a complete sentence, lacking either a subject or a finite verb.
A sentence fragment is anything which does not qualify as a complete sentence under the rules of English grammar, lacking either a subject or a finite predicate. Sentence fragments are considered ungrammatical in running text, but there are many contexts in which fragments are expected or necessary, including titles, headlines, text messaging, conversation, and other places where brevity is more important than completeness.
