'won't' is a contraction of 'will not.' As an auxiliary verb, it is used to indicate a future action that someone is unwilling to perform or a future event that is not expected to happen. It can also express a strong determination not to do something.
'won't' is used to form the negative of the future tense with 'will.' It can also be used to make predictions about the future. Additionally, 'won't' can express refusal or a strong determination.
I won't be attending the meeting tomorrow.
It won't rain today; the sky is clear.
She won't listen to any excuses.
'won't' is the negative form of 'will,' so ensure the context requires a negative expression. It's a common mistake to use 'won't' when expressing a lack of ability. For ability, 'can't' (cannot) should be used. For example, 'I can't swim' (not 'I won't swim') unless you're expressing a refusal to swim. In older English and in some dialects, 'won't' was sometimes used as a contraction for 'want.' However, in modern standard English, this usage is considered archaic or nonstandard.