auxiliary verb

Verb that is used with a ‘main’ verb to help form a specific tense, and also negatives and questions. Meaning a ‘helping’ verb, the auxiliary verbs are to be, to have, and to do, as in ‘That can be changed’, ‘You must have known’, and ‘You do see’.

‘To be’ can be used to form the continuous tenses, as in ‘She is living in England’. It can also be used with a past participle to form the passive voice, as in ‘The boy was drenched in water’.

‘To have’ is used to form the past tense, as in ‘She had finished the letter’.

‘To do’ is used for questions and negatives, as in ‘I don't. Do you?’, and both ‘to be’ and ‘to have’ have similar forms.