Learn English from A to Z

AUXILIARY VERBS

Negatives

Auxiliary verbs (can, may, must, should) are helping verbs that work together with the main verb.
To make them negative, just add not after the auxiliary:

• can → cannot / can’t

• must → must not / mustn’t

• should → should not / shouldn’t

• may → may not (⚠️ no contraction for may)

Examples:

• She can’t swim. (full: She cannot swim.)

• You mustn’t smoke here. (full: You must not smoke here.)

• He shouldn’t be late. (full: He should not be late.)

• She may not come today. (no short form)

Exercises

Change the following sentences from affirmative to negative. Use both the full form and the contracted form (except for may).

1. She can drive a car. (She cannot drive a car. / She can’t drive a car.)

2. They must finish the homework today.

3. You should call your teacher now.

4. He may join us for dinner.

5. We can play football after class.

6. I must wear a uniform at school.

7. They should bring their books tomorrow.

8. You may enter the library.

9. She can speak three languages.

10. We must pay attention in class.