Auxiliary Verbs
English has three auxiliary verbs: be, do, have.


A. Be is used as the auxiliary in continuous tenses and passive voice (in all sentences: affirmative and negative, statements and questions).
Forms without tense:
base: be
ing: being
participle: been
Forms with tense:
present: am, is, are
past: was, were


B. Do is used as the auxiliary in simple past and simple present tenses (in questions and negatives only).
Forms without tense:
base: do
ing: doing
participle: done
Forms with tense:
present: do, does
past: did


C. Have is used as the auxiliary in perfect tenses (in all sentences: affirmative and negative, statements and questions).
Forms without tense:
base: have
ing: having
participle: had
Forms with tense:
present: have, has
past: had


D. Be, do, and have are not always auxiliary verbs. They can also be main verbs. Main verbs are underlined in the examples below.
She is a student. (“is” is a verb)
She is studying English. (“is” is an auxiliary)
She does her homework. (“does” is a verb)
She doesn’t enjoy homework. (“does” is an auxiliary)
Does she get good grades? (“Does” is an auxiliary)
She has a computer. (“has” is a verb)
She has used a computer for three years. (“has” is an auxiliary)