未必【wèibì】

未必 means "not necessarily". It goes before the verb or adjective and casts doubt on what someone assumes, without saying the opposite is true.

It is the same as 不一定 in meaning, and a little more formal. In conversation both are common; in writing 未必 is more usual.

On its own, 未必 or 那可未必 answers a claim with "not necessarily".

未必 does not mean 不

未必 leaves room for yes. 他未必知道 says he may or may not know; 他不知道 says he doesn't.

未必 already contains the negative, so it never takes 不 in front.

• × 他不未必来 → 他未必来 / 他不一定来

未必不 + verb is a double negative, and it leans the other way: 他未必不同意 means he may well agree.