/maIt/ modal verb negative short form mightn't
1 if something might happen or might be true, there is a possibility that it may happen or be true but you are not certain: Who knows - England might win the next World Cup! | "Are you going to write her a letter?" "I might, I might not." | You might not have noticed but I've put up a 'no smoking' sign in here. | Did you see the way he was driving? I might have been killed.2 the past tense of may: Thinking it might rain, I decided to go in the car. | She asked if she might open a window.3 used to give advice or make a suggestion: If the police can't help, you might try the Citizens Advice Bureau. | I thought we might spend the lesson studying irregular verbs.4a) spoken old-fashioned used to ask politely if you can do something: Might I come in?b) might I say/ask/add etc spoken used to politely give more information, ask a question, interrupt etc: Might I just add that Miriam has been a pleasure to work with and we wish her every success in the future.5 used when you are angry or surprised when someone has not done something that you think they should do: You might have cleaned up before you left! | Don't you think he might at least say thank you?6 I might have known/guessed etc spoken used to say that you are not surprised at a situation: Jake Thompson! I might have known you'd be behind all this!7 might well if something might well happen or might well be true you think it is fairly likely to happen or be true: You might well find that you'll need more by the weekend.8 might (just) as well usually spoken used to suggest doing something that you do not really want to do, because you have no better ideas: It's no good waiting for the bus. We might as well walk.9 might...but... used to tell someone that although what they said is true, something else which seemed very different is also a fact: You might be a strong swimmer but that doesn't mean you can win a triathlon.10 formal used to say why something happens or the reason why someone does something: Samuel left his children a letter, so that his family might understand why he had to go away.11 old-fashioned humorous used to politely ask for information: And who might you be, young man?—compare may 1 2 noun (U)1 great strength and power: the full might of the Russian army | with all your might (=using all your strength and a lot of effort): He swung the ax with all his might. | with might and main literary (=with a lot of strength)2 might is right BrE might makes right AmE used to say that powerful people and countries can do whatever they want
Longman dictionary of contemporary English. 2004.