Modal and Auxiliary Verbs

AUXILIARY VERBS

BE, HAVE and DO are auxiliary verbs. Auxiliary verbs are ‘helping verbs’ and are used to give more detail about the main verb.
Examples:

  1. ‘BE’ is used with the Present Continuous tense of the main verb: “I am working”.
  2. “HAVE” is used with the Perfect tenses: “I have been working”, “I had been working”.
  3. “DO” is used to form the Interrogative; both positive and negative: “Do you work?” / “No, I don’t work”.
Things to note about auxiliary verbs:
  • Auxiliary verbs can also be used as main verbs. i.e.
    • I have had a lot of English lessons.. (HAVE is the auxiliary, HAD is the main verb.)
    • How do I do this exercise? (The first DO is the auxiliary, the second is the main verb.)
  • Auxiliary verbs CANNOT be used WITHOUT a main verb.
  • Auxiliary verbs CANNOT be used with modal verbs.
  • Auxiliary verbs are used to form the interrogative (ask questions), and the negative.
  • Auxiliary verbs are often used to change the tense of the main verb.
  • Auxiliary verbs are irregular.
    • BE = I am / you are / he, she, it is / we are / they are.
    • HAVE = I have / you have / he, she, it has / we have / they have.
    • DO = I do / you do / he, she, it does / we do / they do.

 

MODAL VERBS

CAN, COULD / MAY, MIGHT, MUST / SHALL, SHOULD (OUGHT TO) / WILL, WOULD are the modal verbs (known as ‘modal auxiliary’ verbs). They are also ‘helping verbs’, but unlike the three auxiliary verbs above, they cannot be used as main verbs.
Examples:

  1. I can speak a little English. I could speak English if I studied more.
  2. I may learn to speak English. I might learn to speak it well. I must learn English.
  3. I shall learn to speak English. I should (ought to) learn it if I want a better job.
  4. I will learn to speak English. It would be easier if I did more of the lessons on this site.

Things to note about modal verbs:
  • Modal verbs do not add an S to the third person singular. i.e. I can / you can / he, she, it can / we can / they can.
  • Modal verbs don’t need the auxiliary DO to form the interrogative and negative. i.e. Can I speak English?
  • Modal verbs don’t have an infinitive form (except BE ABLE TO and OUGHT TO)
  • The verbs HAVE TO and NEED TO are known as ‘semi-modals’ because they don’t have all the same characteristics as the other modals.

Modal verbs in more detail:
  1. Can / Could are used for requests and to talk about the ability to do something.
    • Can I go to the party, please? (Please allow me to go.)
    • I can go to the party with you. (I am able to go.)
  2. May / Might are used for possibility / probability (improbability) and also for (polite) requests.
    • John may come to the party. (He probably will).
    • John might not come to the party. (He possibly won’t).
    • May I come to the party, please? (Please ask me to come.)
  3. Shall / Should (Ought to) / Must – are used for degrees of obligation.
    • Shall I come to the party with you? (Would you like me to?)
    • Should I come to the party with you? (Do you think it would be a good idea?)
    • Must I come to the party with you? (Is it an obligation?)
  4. Will / Would are used for predictions and conditionals.
    • John will be at the party, I am sure of it. (Prediction)
    • I would go to the party if John were going. (Conditional)

 

Relevant Content:

Wikipedia on Auxiliary Verbs
Wikipedia on Modal Verbs
 

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