Grammar Reference. Unit 1.

1.0 Introduction to auxiliary verbs

There are three classes of verbs in English,

1. The auxiliary verbs do, be, and have

These are used to form tenses, and to show forms such as questions and negatives.

2. Modal auxiliary verbs

Must, can, should, might, will, and would are examples of modal auxiliary verbs. They "help" other verbs, but unlike do, be, and have, they have their own meanings. For example, must expresses obligation and can expresses ability.

3. Full verbs.

These are all the other verbs in the language, for example, play, run, help, think, want, go, etc.

Do, be, and have can also be used as full verbs with their own meanings.

do
I do my washing on Sundays.
She does a lot of business in Eastern Europe.
What do you do? = What's your job? - The first do is auxiliary; the second is a full verb.

be
We are in class at the moment.
They were at home yesterday.
I want to be a priest.

have
He has a lot of problems.
They have three children.

A note on have and have got.
There are two forms of the verb have: have as a full verb with do/does/did for questions, negatives, and short answers and have got where have is an auxiliary.

1.1. Tenses and auxiliary verbs

When do, be, and have are used as auxiliary verbs, they make different verb forms.

do
In the Present Simple and the Past Simple there is no auxiliary verb, so do, does, and did are used to make questions and negatives (except with be / have got).

Where do you work?
She doesn't like her job.
What did you buy?
We didn't buy anything.

be
1. Be + verb + -ing is used to make continuous verb forms. Continuous verb forms describe activities in progress and temporary activities.

He's washing his hands. (Present Continuous)
They were going to work. (Past Continuous)
I've been learning English for three years (Present Perfect Continuous)
I'd like to be lying on the beach right now. (Continuous infinitive)

2. Be + past participle is used to form the passive.

Paper is made from wood. (Present Simple passive)
My car was stolen yesterday (Past Simple passive)
The house has been repainted (Present Perfect passive)
This homework needs to be done tonight (Passive infinitive)

have
Have + past participle is used to make perfect verb forms.

He has worked in several different countries (Present Perfect)
She was crying because she had had some bad news (Past Perfect)
I'd like to have met Napoleon (Perfect infinitive)

In English, Perfect tense means 'before', so Present Perfect means 'before now.' Past Perfect means 'before a time in the past.'