what is a fragment sentence

A sentence fragment is an incomplete sentence that is missing either its subject or its main verb, or it does not express a complete thought. Fragments are usually pieces of sentences that have become disconnected from the main clause. Some fragments occur as the result of simple typographical errors or omission of words, while others are written as main clauses but lack a subject or main verb. To correct a fragment, one can attach it to a nearby complete sentence, revise it by adding whatever is missing, or combine it with the main clause. It is important to avoid sentence fragments in formal situations and academic writing, but fragments can sometimes serve a valid dramatic purpose in journalism, blogging, and fiction writing.