A fragment is an incomplete sentence that is missing either its subject or its main verb, or it does not express a complete thought. It is a group of words that looks like a sentence but cannot stand on its own. Fragments can be caused by the misuse of subordinators, prepositions, or words like "such as, for example, especially," etc. They can also occur as the result of simple typographical errors or omission of words. To fix a fragment, one can attach it to a nearby complete sentence, revise it by adding whatever is missing, or combine it with an independent clause. It is important to avoid sentence fragments in formal situations and academic writing.