Modals - can and could

can and could

Can, could, may, might, must, shall, should, will and would are modal verbs. They are used to express meaning of certainty or obligation and freedom to act.

Subject + modal + base form of second verb

  Modals

Usage

Examples

Remarks

can ability I can hop! Can you hop? present ability

Can I see you next Monday? future ability

possibility I think the computer can be repaired.

The computer can't be repaired. Can't = cannot = not possible

cannot versus may not

permission - informal Can I play computer games? asking for permission

May is traditionally used for permission, can for ability, However, this distinction is fading. In asking permission, can is less formal than may.

Of course, you can play. giving permission

request - informal Can you get me a drink?

offer Can I carry your bags?

"present progressive" I can hear someone knocking on the door. Verbs of perception ( e.g., see, hear, feel, smell and taste ) or verbs that express a state of being or mental activity are not normally used in the progressive form. In place of the progressive form, we use modal + base form e.g., can hear ( or simply hear ) instead of hearing.

could ability

Could is not normally used to talk about real past achievements. Instead, verbs like was/were able, managed or succeeded (in ... ing) are used.

Example: Finally, we were able to ~~could~~ reach the summit of the mountain.

could versus be able to I could run up Mount Faber when I was younger. past ability

Could used as a past tense of can.

I could understand what she said. Could used with verbs of perception and mental activity to talk about past ability for an occasion

present possibility Most accidents in the home could be prevented. logical possibility that something is happening or may be true

unrealized possibility

could have + past participle He could have been the Chief Executive Officer if he had not resigned. Could have used to say that something might have happened but did not happen.

asking for permission
- polite or formal Could I leave early today? Yes, you can ~~could~~ or No, you can't ~~couldn't~~.

Could is not used for giving or refusing permission.

reporting permission
- already given Mum said I could play computer games. Was/were allowed is used to report permission for one particular past action.

Example: Although I didn't finish my homework, I was allowed ~~could~~ to play computer games for an hour.

reported speech "Can I return the dress in a week's time?" asked Jean

Jean asked if she could return the dress next week. Can is changed into could when the reporting verb is in the past tense.

request - polite or formal Could you get me another piece of cake?

suggestion If you got nothing to do, you could stack these books onto the shelves.

conditional If I had a million dollars, I could take my family for a holiday in Europe. Could is used in a conditional sense to mean would be able

  Difference between "could" and "be able to"

I could leave. = I had the opportunity to leave but did not.

I was able to leave. = I had the opportunity to leave and I left.

  In negative sentences ...

can't (couldn't) = it is not possible that something is true.

may not (might not) = it is possible that something is not true.

Main Index | Verbs Index | LESOL © Virtual Teacher Aide

		Subject + modal + base form of second verb
Modals	Usage	Examples	Remarks
can	ability	I can hop! Can you hop?	present ability
	ability	Can I see you next Monday?	future ability
	possibility	I think the computer can be repaired. The computer can't be repaired.	Can't = cannot = not possible cannot versus may not
	permission - informal	Can I play computer games?	asking for permission May is traditionally used for permission, can for ability, However, this distinction is fading. In asking permission, can is less formal than may.
	permission - informal	Of course, you can play.	giving permission
	request - informal	Can you get me a drink?
	offer	Can I carry your bags?
	"present progressive"	I can hear someone knocking on the door.	Verbs of perception ( e.g., see, hear, feel, smell and taste ) or verbs that express a state of being or mental activity are not normally used in the progressive form. In place of the progressive form, we use modal + base form e.g., can hear ( or simply hear ) instead of hearing.
could	ability Could is not normally used to talk about real past achievements. Instead, verbs like was/were able, managed or succeeded (in ... ing) are used. Example: Finally, we were able to ~~could~~ reach the summit of the mountain. could versus be able to	I could run up Mount Faber when I was younger.	past ability Could used as a past tense of can.
		I could understand what she said.	Could used with verbs of perception and mental activity to talk about past ability for an occasion
	present possibility	Most accidents in the home could be prevented.	logical possibility that something is happening or may be true
	unrealized possibility could have + past participle	He could have been the Chief Executive Officer if he had not resigned.	Could have used to say that something might have happened but did not happen.
	asking for permission - polite or formal	Could I leave early today?	Yes, you can ~~could~~ or No, you can't ~~couldn't~~. Could is not used for giving or refusing permission.
	reporting permission - already given	Mum said I could play computer games.	Was/were allowed is used to report permission for one particular past action. Example: Although I didn't finish my homework, I was allowed ~~could~~ to play computer games for an hour.
	reported speech	"Can I return the dress in a week's time?" asked Jean Jean asked if she could return the dress next week.	Can is changed into could when the reporting verb is in the past tense.
	request - polite or formal	Could you get me another piece of cake?
	suggestion	If you got nothing to do, you could stack these books onto the shelves.
	conditional	If I had a million dollars, I could take my family for a holiday in Europe.	Could is used in a conditional sense to mean would be able