Explanations answer or anticipate questions about why something happened or why something is as it is. Such questions are often difficult to answer, for they require us not only to think of an explanation, but to think of one that will satisfy the questioner. I shall not attempt here to evaluate the satisfactoriness of various types of explanation. Rewarding though such an investigation would undoubtedly be, its very initiation depends upon the prior resolution of a more mundane descriptive problem: which utterances should be classified as explanations—however unsatisfactory they may be—and which should be classified as something else? It is with this problem that I shall be concerned in this paper—with a search for formal properties that distinguish explanations from other kinds of utterance such as simple statements.