An auxiliary is a verb used with the main verb to show the tense and to form the questions and negative.
(a)I shall help my friends.
(b)Do you go to school daily?
(c)He did not act upon my advice.
There can be two kinds of auxiliaries.
1. Primary Auxiliaries; as- is, am, are, was, were, do, does, did, has, have, had.
2. Modal Auxiliaries; as – will, shall, would, should, can could, may, might, must, ought to.
Note the difference between Primary Auxiliaries and Modal Auxiliaries.
1. Primary auxiliaries can be used independently as a Principle verb also. For example:
He is a rich man.
Modal auxiliaries can not be used independently as a Principle verb also. For example:
He will go.
2. Primary auxiliaries change their form according to the person and number of the subject. For example:
He is going home.
They are going home.
Modal auxiliaries do not change according to the person and number of the subject. For example:
He will study hard.
They will study hard.
3. Primary auxiliaries (be, do, have) can take infinitive (to + verb) form. For example:
She wants to do it.
Modal auxiliaries can not take infinitive form; we cannot say to will, to can, to may, to must etc.
4. We can add – ing to the Primary auxiliaries be and have. For example:
Being tired, I went to home.
Having passed, she became happy.
But we cannot add – ing to Modal auxiliaries.
5. Modal auxiliaries take with them only the root form of the verb.
I will go home.
They must go home.
But we cannot use the root form of the verb with the Primary auxiliaries. For example:
They have gone home.
We are doing our homework.
Examples of Primary auxiliaries
1. He is working very hard.
2. Does she go to school daily?
3. They are very good students.
4. I am not very happy.
5. I had already done my work.
Examples of Modal auxiliaries
1. We ought to help the poor.
2. He cannot hear.He is deaf.
3. You must consult some good doctor.
4. Will you see the parrot in that tree.
5. May I use your telephone.