Subject and object questions

Who and what can ask about the subject (who or what does the action) or the object (who or what receives it). The two kinds are built differently.

• Subject question: Who / What + verb (like a statement). No do / does / did.
• Object question: Who / What + do / does / did + subject + base form — like a normal question.

The question word takes the subject's place, so the word order stays the same as in a statement: just replace the subject with who / what. The verb keeps its tense — -s in the present simple, the past form in the past.

• Who lives in that big house on the corner?

• What happened? Why is everyone shouting?

• Who taught you to swim?

• Which bus goes to the airport?

• How many people came to the party?

• The same goes for which / whose / how many + noun when that phrase is the subject.
• Who / what as the subject usually take a singular verb, even if the answer is several people: Who wants more rice? (not Who want…?).
• The auxiliary that belongs to the tense stays; you just don't add do / does / did: Who is coming tonight? · Who can help me? · Who has seen my keys?

When the question word is the object, the question is built like any other: question word + auxiliary + subject + verb. In the simple tenses the auxiliary is do / does / did.

• Who did you meet at the party?

• What did you buy at the market yesterday?

• What does this word mean?

• Who are you waiting for?

If the question word is the object of a preposition, the preposition usually goes at the end: Who are you talking to? What are you looking at? To whom…? is only for formal writing.

• Who told you? — My sister told me.

  asking about the teller

• Who did you tell? — I told my sister.

  asking about the listener

• What made you so angry?

• What did you make for dinner?

💡Ask yourself: is the question word the doer? If yes (Who called you?), there is no do / does / did. If someone else is the doer (Who did you call?), put do / does / did before that person.

💡You may sometimes hear Who did break it? with a stressed did — when arguing or insisting on an answer. That is special emphasis; a normal subject question has no did.

• ✗Who did break the vase?

  ✓Who broke the vase?

  Subject question: no did.

• ✗What did happen to your car?

  ✓What happened to your car?

  What is the subject: no did.

• ✗Who live next door to you?

  ✓Who lives next door to you?

  Who as the subject → singular verb with -s.

• ✗Who you are waiting for?

  ✓Who are you waiting for?

  Object question: the auxiliary goes before the subject.

• ✗Who you called last night?

  ✓Who did you call last night?

  An object question in the past simple needs did.

• ✗What did make you so angry?

  ✓What made you so angry?

  What is the subject: no did.