Auxiliary Verbs

An auxiliary verb or 'helping' verb, is combined with the principal verb to form certain tenses or moods. (See also modal verbs)
The only true auxiliary verbs in English are 'to be', 'to have', and 'to do'.

'To be' is an auxiliary verb for the continuous tenses (the present continuous, the past continuous, the future continuous):

• I am going home.

• She was fishing with her father.

• We will be calling on you later.

'To have' is an auxiliary verb for the perfect tenses, including the present perfect, the past perfect, the future perfect and the past (3rd) conditional:

• We have finished.

• They hadn't waited for us.

'To do' is an auxiliary verb for making questions and negations in both the present and past simple:

• Do you have any money?

• Did you hear me?

• He doesn't want to help us.