A question may be either a linguistic expression used to make a request for information, or else the request itself made by such an expression. This information is provided with an answer.

Questions are normally put or asked using interrogative sentences. But they can also be put by imperative sentences, which normally express commands: "Tell me what 2 + 2 is"; conversely, some expressions, such as "Would you pass the butter?", have the grammatical form of questions but actually function as requests for action, not for answers. (A phrase such as this could, theoretically, also be viewed not merely as a request but as an observation of the other person's desire to comply with the request given.)

Varieties of questions

Questions have a number of uses. 'Raising a question' may guide the questioner along an avenue of research (see Socratic method). A rhetorical question is asked in order to make a point, and does not expect an answer (often the answer is implied or obvious). Pre-suppositional questions, such as "Have you stopped beating your wife?" may be used as a joke or to embarrass an audience, because any answer a person could give would imply more information than he was willing to affirm. Questions can also be titles of works of art and literature (e.g. Leo Tolstoy's short story How Much Land Does a Man Need? and the movie What About Bob?). McKenzie lists 17 types of questions in his "Questioning Toolkit" and suggests that thinkers must orchestrate and combine these types in his article "Punchy Question Combinations". Examples of his question types include the irreverent question, the apparently irrelevant question, the hypothetical question and the unanswerable question.

In research projects

1. Descriptive question, used primarily to describe the existence of some thing or process.
2. Relational question, designed to look at the relationships between two or more variables.
3. Causal question, designed to determine whether one or more variables causes or affects one or more outcome variables.

In surveys (there are a few types of questions)

1. Dichotomous questions, usually these questions require yes/no answers or require a person to answer by choosing an option(s) from a multiple choice of possible answers.
2. Nominal questions, these types of questions are designed to inquire about a level of quantitative measure. Usually these questions form correlations between a number and a concept. For example:

Occupational Class: 1= Moderate 2= Severe 3= etc.

1. Qualifying questions (a.k.a. filter questions, or contingency questions) These types of questions are designed to determine if the individual answering the question needs to continue on to answer subsequential questions.