A single sentence can express many different things. Here is one way to divide different types of sentences into four main categories.
When we use language, we do it for a purpose. The purpose may be
A to tell somebody something (to give information)
B to ask somebody a question (to request information)
C to ask somebody to do something (to request action)
D to promise somebody to do something (to promise something)
These very broad and crude categories can be linked to different sentence types. Here is a simple table:
| Example | Sentence type | Form | What it does |
|---|---|---|---|
| I have sent the letter | declarative | normal word order | gives information |
Have you sent the letter? or When did you send the letter? | interrogative | inverted word order | asks for information, either 1) a yes/no answer or 2) specific information |
| Send the letter | imperative | no subject | demands action |
| I'll send the letter | declarative | no typical form, will is often used | commits speaker to act |
Since language is so flexible, the rules which link the form of a sentence to its function- as we have done above - have very many exceptions.
Here is one: A request for action is not often expressed in a blunt imperative, but rather in some roundabout way. Could you send the letter?/Do you mind sending the letter?/Is it possible for you to send the letter? The request should at least be softened by a please. Please send the letter.
Despite such exceptions, the basic correlation is that declaratives provide information, interrogatives demand information and imperatives demand action. Here is a short news text for illustration.
The court decided to postpone the proceedings and meet again tomorrow. The evidence is slim and a long trial would have unfortunate consequences in this case. Would it be wiser to drop the charges altogether?
The last interrogative appeals to the reader. He/She is not being told the view of the newspaper, but rather asked to answer a question. In that sense the interrogative is interactive because it brings the reader into the text.
In addition, questions may have a rhetorical effect. That means they are not real information-seeking questions, but questions that lead the reader to agree with the paper’s view. [Yes, it is wiser to drop the charges.] Interrogatives may have this effect, but we cannot tell for sure because we do not have the wider context.
