The auxiliary verbs—those words which may be added to the principal parts to form verb phrases — belong to a specific and limited group. The verb forms listed below are those which can be used to begin a verb phrase:

do            can          am           have

does        could       are           has

did           shall        is             had

may         should     was

might       will          were

must        would

The verbs in the Jirst two columns combine only with the naming form of the verb: e.g., go, break, freeze, see, take:

• She didn't go to the party.
• It may break any minute.
• You will freeze without a coat.
• We could see the distant mountains.
• I can take another passenger.

In the passive voice the auxiliaries in this group combine with the naming form of the verb be, followed by a past participle: e.g., may be broken, will be frozen, could be seen. The verbs in the third column can combine with the present participle: e.g., choosing, singing, speaking:

• He is choosing his words carefully.
• The tenors are singing off key.
• We were speaking together recently.

The verbs in the third and fourth columns can combine with the past participle: e.g., broken, forgotten, slain, written:

•  The dam is broken.
• All their good intentions were forgotten.
• He has slain his friend.
• We had received several letters from her.

The words in the last two columns—the forms of the verbs be and have—are the most common auxiliaries. Verb phrases of three or four words are formed by using combinations of these between the first auxiliary and the main verb form: must be taken, will have been chosen, is being written, might have seen, will be working, should have been going.