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do: auxiliary verb

The auxiliary verb do is followed by infinitives without to. It has several uses.

Questions​

We use do to make questions with ordinary verbs, but not with other auxiliary verbs (see here). Compare:

  • Do you like football? (not Like you football?)
  • Can you play football? (not Do you can play football?)

The auxiliary do can make questions with the ordinary verb do.

  • What do you do in the evenings?

Negatives​

We use do to make negative clauses with ordinary verbs (including the ordinary verb do), but not with other auxiliary verbs (see here).

  • I don’t like football. (not I like not football.)
  • Don’t go.
  • I don’t do much in the evenings.
  • but I can’t play football. (not I don’t can play football.)

Emphasis​

We can use do in an affirmative clause for emphasis.

  • Do sit down.
  • You do look nice today!
  • She thinks I don’t love her, but I do love her.
  • I don’t do much sport now, but I did play football when I was younger.

Inversion​

Do is used in some structures with inversion (verb before subject) (see here).

  • At no time did he lose his self-control.

Ellipsis​

In cases where an auxiliary is used instead of a whole verb phrase (see here), do is common in affirmative clauses as well as questions and negatives.

  • She doesn’t like dancing, but I do. (= … but I like dancing.)
  • ‘That meat smells funny.’ ‘Yes, it does, doesn’t it?’
  • Anna thinks there’s something wrong with James, and so do I.
note

For do with be, (see here).

For weak pronunciations of do and does, (see here).

For do in short answers, (see here).