A sentence fragment occurs when you punctuate a partial sentence as if it were a complete sentence. Sentence fragments are missing a subject or a predicate (verb or verb phrase)--and sometimes both.
Common fragment errors occur when...
A verb is missing
Fragment: The foremost leader of the free world.
Correct: The foremost leader of the free world signed a treaty to ban the testing of nuclear weapons.
A subject is missing
Fragment: Separated visible light into a spectrum of color.
Correct: Isaac Newton separated visible light into a spectrum of color.
Relative pronouns, subordinating conjunctions, or verbal phrases begin a clause, creating an incomplete thought
Relative pronouns (that, which, whichever, who, whoever, whom, whomever) signal a clause that needs the rest of the sentence to complete the thought and make sense. Don't let a phrase beginning with a relative pronoun stand alone.
Fragment: People who work the night shift at factories.
Correct: People who work the night shift at factories have to adjust to sleeping during the day.
Subordinating Conjunctions and Conjunctive Adverbs
Subordinating conjunctions and conjunctive adverbs combine an incomplete thought or phrase to a complete sentence. If you let the phrase stand alone, you create a sentence fragment.
Fragment: Although people may feel discouraged about the presidential debates.
Correct: Although people may feel discouraged about the presidential debates, they still should vote in the next election.
Subordinating conjunctions: after, though, although, assuming that, if, until, before, provided that, as if, while, since, because, how, unless, where, whenever
Conjunctive adverbs: though, although, therefore, however, whereas, nevertheless, also, otherwise
Verb phrases are verb forms that function as subjects, objects, or modifiers. Verb phrases become fragments when they are not attached to a main sentence.
Fragment: Mountain biking through the Allegheny foothills.
Correct: I went mountain biking through the Allegheny foothills.