Not necessarily / may not (未必)

Structure 未必 + (claim being challenged)

未必 (wèibì) cautiously negates someone else's certainty: «not necessarily, it needn't be so». It refutes an inference taken for granted without fully denying it: 贵的未必就是好的 = «expensive isn't necessarily good». Its lower-level neighbour is 不见得 (HSK 4), same meaning but more colloquial; 未必 is distinctly more cultivated, at home in essays and the press. It often precedes 就/会 and leaves room for the exception.

Examples

贵guì的de未wèi必bì就jiù是shì好hǎo的de。
Expensive isn't necessarily good.
多duō数shù人rén赞zàn成chéng的de，未wèi必bì就jiù是shì正zhèng确què的de。
What the majority approves of isn't necessarily right.
努nǔ力lì了le未wèi必bì成chéng功gōng，但dàn不bù努nǔ力lì一yī定dìng失shī败bài。
Hard work may not bring success, but no effort guarantees failure.
他tā的de看kàn法fǎ未wèi必bì正zhèng确què，值zhí得de商shāng榷què。
His view isn't necessarily correct and is open to debate.

Levels are indicative: they follow the standard Chinese Grammar Wiki (AllSet Learning) progression, not an official HSK 3.0 mapping. We never assign levels by eye.

This point and the other 370, with audio on every example, inside Wanyu.