While each word has its own distinct uses, ‘might’ is the past participle of ‘may’, while ‘could’ is the past participle of ‘can’. They are used in different contexts to convey slightly different meaning. They are used to express possibility, prediction, speculation and necessity.
Form of can/could may/might
Can/could may/might: positive and negative
He / She / It
can / could
can't / couldn't
dance (base form of the verb)
may / might
may not / might not
Can / Could May / Might: Questions
|Can / Could||
he / she / it
dance (base form of the verb)?
|May / Might|
Uses of can/could may/might
Can is designed to suggest ability, permission and an offer. It can be part of a statement or used as a question.
Daniel can dance. (Ability)
Can Daniel go to the dance? (Permission)
Can I take you to the dance? (Offer)
Judy can sing. (Ability)
Can Judy visit your recording studio? (Permission)
Can I help you? (Offer)
Could, alternatively, denotes possibility, requests, permission and past abilities.
There are many ways in which the story could be true. (Possibility)
Daniel could dance as soon as he was able to walk. (Past Ability)
Could you teach Daniel how to do a foxtrot please? (Request)
Judy could sing this song if she had the music (Possibility)
Judy could always hit the high notes, even when she was a little girl (Past Ability)
Could you show Judy how to get to the music hall for her singing lesson? (Request)
May is used when the speaker wishes to suggest possibility or permission.
The audience may stay and watch the main act if Daniel impresses them enough. (Possibility)
May I watch you dance, Daniel? (Permission)
Judy’s singing may be enough to attract a large crowd to the concert tonight. (Possibility)
May I hear you sing another song, Judy? (Permission)
Might is used in order to suggest a diminished possibility or as a past form of ‘may’ when used in
Daniel might win over a number of his critics tonight with his dancing. (Slight Possibility)
The best dancers in the country said they might come and watch Daniel on the stage. (Past version of ‘may’)
Judy’s singing might win her a lucrative recording contract tonight. (Slight Possibility)
A lot of people suggested that they might come and watch Judy perform all of the songs she knows. (Past version of ‘may’)
Can/could may/might: be careful!
These words are collectively known as modal verbs, which means that they are to be used, generally, in conjunction with other verbs. They are used to alter the meaning of the other verbs, changing it to something other than a simple truth.
‘May’, ’might’ and ‘could’ can all be used to suggest possibility. In these contexts, any of the three words will suffice.
‘May’ and ‘might’ can also be used to suggest that whilst one there is one fact, there could well be another which is equally as valid.
‘May’ and ‘can’ are both used in order to demonstrate that something is permissible, though ‘may’ is the more formal option. It is often held that only ‘may’ is used with regards to permission and that ‘can’ is used with regards to ability, though both are often used in an interchangeable manner.
It is common to use all of ‘can’, ‘may’ and ‘could’ for requests. Again, ‘may’ is the more formal option, while it is more commonplace to hear ‘can’ and ‘could’ used in speech.
Many intermediate users struggle with the concept of the interchangeable words despite one (might/could) denoting a past tense version of the partner word. In these instances, the correct use can lead to the sentence sounding more formal.
It should be noted that, as well as being used in an interchangeable fashion in many contexts, ‘might’ is the past tense of ‘may’, while ‘could’ is the past tense version of ‘can’. However, in terms of ‘may/might’, many people also use the term ‘may have’ in order to express a past tense version of ‘may’, with the former being a more formal version.
In some contexts, the differences between ‘may/might’ and ‘can/could’ will only be apparent via reported speech. This is used to indicate that the past participle is being used, though during regular speech and usage the words are almost interchangeable.