Form of the question: declarative statements, prescriptions, declaration of perplexity, obviously incorrect suggestions, invitations to elaborate, deliberate silence, unfinished sentences, gap sentences. Focus of the question: global vs. specific question, language vs. real life. Possible answers to the questions: polar vs. alternative vs.wh-questions, convergent vs. divergent questions. Communicative value of the question: display vs. referential questions, echoic vs. epistemic questions. Nature of thinking questions: literal vs. inference vs. background questions, low order vs. high order questions.