Auxiliary Verbs : To do

The conjugation of to do is as follows:

Present Simple Past Simple
Singular Plural

Affirmation

Singular + Plural

Negation

Singular + Plural

I do
you
he does
she
it
we do
you
they
I didn't
you
we
you
they
we
you
they
I didn't
you
we
you
they
we
you
they
Negation
I don't
you
he doesn't
she
it
we don't
you
they

The uses of to do as an auxiliary verbs are:

a) Formation of questions and negative sentences

  • I don't see anything.
  • I don't think you know me.
  • Does she go to her gymnastic classes on Mondays?

b) Formation of negative imperative sentences.

  • Don't go there.
  • Don't let him go out so late.
  • Don't go. Stay at home and rest up.

Note: if you want to be really polite, you can use do in positive imperative sentences too.

  • Do come.
  • Do be quiet.
  • Do sit down.

c) Emphasis, used to stress what we're saying.

  • I do think he is foolish.
  • Do come in!