Possibility
When we talk about possibility, we usecan, couldandmay,but they are different in meaning.
| This expresses what the speaker believes is a general truth or known fact, or a strong possibility. |
| This does not express a general truth. The speaker is only expressing a weak possibility. |
| This expresses a real fact using the present simple. The speaker is certain and no modality is used. |
See also:
Could
May
Permission
We usecan, couldandmayto ask for permission. We usecanandmay, but notcould, to give permission.Mayis less common:
asking for permission | formal/polite? | giving permission | formal/polite? |
| informal | Yes, you can. Yes, you may. Yes, you could. | informal |
| more formal/polite | formal/polite | |
| even more formal/polite |
See also:
Might
Requests
When we make requests, we can usecanorcould(but notmay).Couldis more polite thancan:
Canyou call back later? I’m busy now.
Couldyou call back later? I’m busy now.
Teachers and parents often usecanandcouldin requests:
Canyou open you books at page 34, please.
Canyou please refrain from chewing gum.
Couldyou just sit down and listen!
See also:
Requests
Politeness
Can,couldormay: typical errors
Couldin the present only expresses weak possibility.Canexpresses strong possibility:
Icantravel in July because my exams will definitely be finished at the beginning of that month.(strong possibility)
Icouldtravel in July because my exams will probably be finished at the beginning of that month.(weak possibility)
We don’t normally usecouldto talk about general truths which refer to thepresent time. We usecaninstead:
Not everyonecanafford to buy organic food.
Not:Not everyone could afford…
We usecould, notcan, to express future possibility.Canexpresses that we are certain of something:
Working in London next summercouldbe a great experience.(The speaker thinks this is possible, in particular circumstances)
Not: …can be a great experience.