Degrees of Certainty

Sometimes, the choice of modal can suggest how probable we think the possibility is. This is not a strict rule, but a general guide.

may: Often suggests a reasonable possibility (e.g., a 50% chance).

might: Can suggest a slightly smaller possibility (e.g., a 30% chance). It is very common in everyday speech.

could: Is often used when suggesting one of several possibilities. It does not mean past ability here.

Negative Forms: may not & might not

We use may not and might not (or mightn’t) to talk about a negative possibility.

Important: We do not use couldn’t to talk about a future possibility. Couldn’t is used for past ability or for deduction (certainty that something is not true).