Geoff Pullum has a good mythbusting description of sentence types on the Lingua Franca blog.
Grammar books, and hundreds of websites out there, are appallingly confused about statements, questions, orders, and exclamations. Most of the problem lies in their failure to distinguish syntax from semantics. I want to try and sort things out a bit, and provide a little homework exercise.
Clause type is syntactic, not semantic. It shouldn’t be confused with any element of meaning or use. Standard English has four clause types (five if you treat 2a and 2b as separate), differing with respect to which words you put where:
Declarative Characteristic use: making statements. Example: He was polite. Key syntactic properties: subject precedes auxiliary and/or predicate.
Interrogative Characteristic use: asking questions.
Closed interrogative: for expressing questions having a fixed, finite list of answers that the form of the question suggests. Example: Was he polite? Key syntactic properties: auxiliary before subject.
Open interrogative: for expressing questions having an unbounded range of answers. Example: How polite was he? Key syntactic properties: wh-phrase at beginning of clause; auxiliary before subject if wh-phrase is not the subject of its clause.
Imperative Characteristic use: issuing directives about desired behavior by others. Example: Be polite. Key syntactic properties: plain form of verb; subject often missing.
Exclamative Characteristic illocutionary force: making exclamatory statements. Example: How polite he was! Key syntactic properties: wh-phrase at beginning of clause (headed by either how or what); subject before auxiliary.
Crucially, the characteristically associated meanings are only a default. Using an interrogative (e.g., What’s your name?) is the stereotypical way to express a question, but declaratives can also in effect convey questions, through a combination of literal meaning and pragmatic implication:
I want to know your name. I’m asking you to tell me your name.
Imperatives, too, can be used to convey the effect of questions:
Tell me your name. Tell me what your name is.
Even an exclamative can come pretty close to implying a question:
How I’d love to know what your name is.
Grammar books and grammar websites are particularly confused about exclamatives, which they often call “exclamatory sentences” (see the hopelessly confused page here for a random example). They imagine that any kind of sentence that might intuitively be used for exclaiming and/or ends with ‘!’ must belong, so they give examples like I can’t figure this out! (a declarative), or Out of my way! (not a clause at all).
Read the whole thing.
I’m a bit surprised that conditionals, subjunctives, counterfactuals and that whole set of commonly confused terms didn’t make the list, but perhaps that’s a topic for next week’s post.