Non-declarative sentences such as interrogatives, imperatives and exclamations are analyzed together as a single class. The author gives a general characterization of all three types and shows that there are no other types of non-declarative sentences. Definitions are offered for the notions of declaration and presupposition. These definitions are applicable to all types of sentence, both declarative and non-declarative. A defining characteristic of non-declarative sentences is that only strongly intensional operators can apply to them to form complex sentences. It is shown that this property of non-declaratives implies that such sentences do not have declarations. A particular case of the relation between questions and conditionals is studied in more detail.