She may not be Anil's sister.
She might not be Anil's sister.
What's the difference?
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Sign up to join this communityExplanation for the examples given in the question:
May and might are used interchangeably, when expressing a possibility or uncertainty (a situation when we are not sure of something). This is the case in your example. We might imagine a conversation that goes like this:
A: Anil's sister came to pick up his things. Where did you put them?
B: Have you checked her ID? She may/might not be Anil's sister.
So, speaker B is not sure whether the visitor is Anil's sister.
In a different situation the same interchangeable usage would apply:
A: Who is that girl in a blue dress?
B: She may/might be Anil's sister.
Again, B is guessing, but isn't sure.
Some sources suggest that usage of may/might implies equal probability (in this example it is equally possible that the girl is or is not Anil's sister).
Other sources state that if something is less likely you should use might and if it's more likely you should use may (but this is a flexible rule).
In formal or academic language, may should be used to express possibility:
A Giant sequoia tree may reach the height of 85 meters.
Other cases where may and/or might are used:
May I help you?
is far more common than 'Might I help you' and can be considered idiomatic.
Next time you might try... You may want to consider...
You may not borrow the car until you can be more careful with it.
Note that this is not likely to be the case with your examples; nobody can forbid someone to be someone else's sibling (such situation would be rather absurd).
You may enter.
Again, this is not the case when you say: 'She may be Anil's sister' - in that sentence nobody is giving her the permission to be Anil's sister; they are speculating who the girl is.
She asked whether she might get a few days off.
I think that comment may/might have offended some people.
If they had lived in another time, their lives might have been different.
may as well/might as well, where both are common; or be that as it may which you should probably use instead of 'be that as it might' since the former is considerably more common
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