Question formation is the set of grammatical operations that turn a statement into an interrogative, built mainly on subject-auxiliary inversion and do-support. English signals most questions by moving an auxiliary in front of the subject, a special case of the broader Inversion system, rather than by intonation alone.
When the clause already contains an auxiliary or modal, that operator simply moves ahead of the subject: She is leaving → Is she leaving?; They can swim → Can they swim?. When there is no auxiliary, English inserts the "dummy" operator do/does/did to carry tense and inversion, while the main verb returns to its base form: He plays tennis → Does he play tennis?. Tense and number are marked once, on the operator, which connects question formation to Subject-Verb Agreement.
| Type | Answered by | Structure | Example |
|---|---|---|---|
| Yes/no | yes or no | operator + subject + verb | Did you see it? |
| Wh- | information | wh-word + operator + subject + verb | Where did you go? |
Wh-words (who, what, which, when, where, why, how) front the questioned element, with inversion following.
When the wh-word is the subject, there is no inversion and no do-support, because nothing needs to move past the subject, the wh-word already occupying subject position: Who came?, What happened?, Which team won?. Compare Who did you see? (object question, inversion) with Who saw you? (subject question, no inversion). This asymmetry is a frequent learner error (Who did come?).
A question tag is a short interrogative appended to a statement, formed from the operator plus a pronoun, and reversing polarity: positive statement takes a negative tag (You're coming, aren't you?), negative takes positive (She didn't call, did she?). Tags check agreement or invite confirmation, and their meaning shifts with intonation: a falling tone expects agreement, a rising tone genuinely asks.
Negative questions (Don't you like it?, Isn't it lovely?) typically carry an attitude (surprise, persuasion, or a request for confirmation) rather than neutral inquiry. The contracted n't sits with the operator before the subject (Why didn't you tell me?).
When a question is embedded inside another clause, the inversion is undone and the word order reverts to statement order: Where is he? → I wonder where he is.; Did she leave? → Do you know whether/if she left?. Embedded yes/no questions use if or whether. This is the same word-order shift seen when questions become reported, and learners who keep the inversion (I wonder where is he) make a recurrent error.