The verbs be (am, is, was), have and do, when used with ordinary verbs to make tenses, passive forms, questions and negatives, are called auxiliaries. Auxiliary verbs are known as helping verbs and are always placed before the main verb. Only when the main verb is implied or already understood, will the auxiliary verb appear alone.
There are three different kinds of auxiliaries:
Be – is, are, am, was, were, being, been: These forms of ‘Be’ are called Auxiliary when used:
1. A) in the formation of continuous tenses; as,
I am preparing dinner.
B) In the formation of the passive voice; as,
She was given an award
2. . It is used as a verb of incomplete prediction; as,
The man is very pompous.
Have- has, have, had
1. . The auxiliary ‘have’ is used in the formation of the perfect tenses; as,
The child has finished the food.
2. It is used to indicate possession; as,
How many files have you in your drawer?
3. It is used as ‘get, receive or take’; as,
We have lunch around 2 p.m.
Do- do, does, did
1. ‘Do’ is used as a principal verb; as,
Do (= perform) meet the boss in 15 minutes.
You do (= act) as they say.
2. As an auxiliary verb; as,
Do you like spinach?
3. For emphasis; as
Please do take the book.
4. As a substitute for other verbs except the verb ‘to be’; as,
She earns more than I do.