An interrogative sentence is a °sentence that can express a °question speech act but not a °statement.
interrogative (a.k.a. question) (INF/CXN) = a speech act which requests information, usu- ally of the addressee, regarding uncertain or unknown information that is part of the propositional content of the question; and the construction that expresses this speech act. Interrogatives are divided into polarity questions, information questions, and alternative questions. (Sections 12.1, 12.3)