Fragments are parts of sentences that the writer has punctuated as if they were complete sentences. They do not, however, express a complete idea.

We start getting everybody up at six in the morning. Even the residents who want to keep sleeping.

I saw the band Vogon Soup about three years ago when they were playing at Hooper’s. And again the next year, when they put on a spectacular show.

Such careless use of fragments makes the writer seem unskilled. Often, all the writer needs to do to correct the problem is attach the fragment to the previous or next sentence:

We start getting everybody up at six in the morning, even the residents who want to keep sleeping.

In other cases, it’s easier or clearer (or both) to change the wording of the fragment so that it stands on its own as a sentence:

I saw the band Vogon Soup about three years ago when they were playing at Hooper’s. I saw them again the next year, when they put on a spectacular show.

Everyday speech is full of fragments, particularly in answer to questions — fragments like Not me, Over here, and Because I said so! Since fragments are conversational, they often appear in dialogue in journalism and fiction, and in advertising as well. But in academic writing, fragments suggest that the writer either doesn’t know what a proper sentence is or couldn’t be bothered to read his own draft and revise it.