Auxiliary Verbs "Can/Could" and "May/Might/Must"

top deco

Auxiliary Verbs - 'Can/Could,' 'May/Might/Must'


Used to express ability (to be able to do something) :
  • I can make jewelry.
  • He can't speak French.
  • Can you open this jar?
Used to ask for permission:
  • Can I use your bathroom?
  • Can I leave now?
  • Can I raise the volume?
Used to make requests or suggestions:
  • Can I have more napkins?
  • Can I have the bill?
  • You can take this spot if you like.
  • You can do whatever you want.

Could (past form of can)

Describes an ability that someone had in the past:
  • I could swim when I was young.
  • You could see the boat sinking.
  • They could tell he was nervous.
Often used in auxiliary functions to express permission politely:
  • Could I take this jacket with me?
  • You could borrow my umbrella.
  • Could you please let me pass you?
  • Could I get you more water?
Used to express possibility:
  • All of them could ride in the van.
  • You could always stay at our house.
  • Could it be true?
  • This plan could really work out.


Used to ask for formal permission:
  • May I come in?
  • May I say something now?
  • May I ask one question?
Used to suggest something that is possible:
  • She may agree with this plan.
  • They may not be happy about what happened.
  • It may shower tonight.

Might (past form of may)

Used to suggest a smaller possibility than may does (actually, might is more common than may in American English) :
  • He might have finished it.
  • I might go see a doctor.
  • I might not come this time.
  • It might be right.
  • You might have lost it.
  • The store might have been closed today.


Used to express something formally required or necessary:
  • I must complete the project by this week.
  • The government must provide health care for everybody.
  • Everyone must save the natural resources of the earth.
  • The building must have a fire alarm.
  • You must answer my question right now.
Used to show that something is very likely:
  • He must be a genius.
  • You must be joking!
  • There must be an accident.
  • She must be very tired.

[Quiz 21.1]

Choose the right word for each blank.

1) She                      (can, could, may, might, must) have Practice English dialogues aboutd a lot. Her performance was amazing.
2) I can't find my watch anywhere. I                      (can, could, may, might, must) have lost it.
3) Professor,                      (can, could, may, might, must) I ask a question?
4)                      (can, could, may, might, must) you please lower your voice?
5) You                      (can, could, may, might, must) be kidding! How is that possible?
6) I                      (can, could, may, might, must) speak both English and Chinese fluently.

previous lessonnext lesson
bottom deco