Auxiliary verbs, sometimes called helping verbs, help complete the form and meaning of main verbs. The auxiliary verbs include the modal verbs, the primary verbs, and a few special verbs like dare and need. The modal verbs are can, could, may, might, must, shall, should, will, and would. They are called modal because they express the mood of verbs (for more on this, see
verbs, mood of and
subjunctive). The primary verbs are be, do, and have. The primary verbs have the distinction of being able to function either as main verbs or as auxiliaries.
1
The auxiliary verbs differ from main verbs in the following ways:
They do not take word endings to form participles or agree with their subject. Thus, we say She may go to the store, but never She mays go to the store.
They come before not in negative clauses, and they do not use do to form the negative: You might not like that. A main verb uses do to form the negative and follows not: You do not like that.
They come before the subject in a question: Can I have another apple? Would you like to go to the movies? Main verbs must use do and follow the subject to form questions: Do you want to go to the movies?
They take the infinitive without to: I will call you tomorrow. A main verb that takes an infinitive always uses to: I promise to call you tomorrow.
2
When functioning as auxiliary verbs, the primary verbs serve the following functions. Be shows continuing action (We are working on a new plan) and forms the passive voice (The shed was destroyed in the storm). Have is used to make perfect tenses—tenses that show completed action (She has finally finished her book. Have you ever gone windsurfing? We had planned to go out tonight). Do is used to form negatives (I do not wish to offend you), to ask questions (Do you ever write to her?), to show emphasis (I do want you to come to the party), and to stand for a full verb in certain other constructions (She likes jazz more than he does).
3
In their capacity as auxiliaries, the primary verbs retain some features of main verbs. All the primary verbs can change form to agree in number with their subject. We say I am going, He has eaten, and She does not travel much. Have and be can form participles and still play an auxiliary role in a verb phrase: Having finished in the garage, he went home. They did not give up even when being badly outplayed. Have and be are used with participles and cannot take an infinitive without to.
4
As main verbs, have and be present certain exceptions to the criteria stated in rules two and four above. They can come before not in negative sentences (We haven’t any pickles. He is not there). They can also appear before the subject in questions (Is anybody home? Have you no shame?). It just goes to show that even the most basic words can turn out to be quite complex once you examine how they are used.
