未必 (wèi bì): not necessarily, may not

This restaurant has great reviews, but it may not suit everyone's taste; you'd better look at the menu first.

Although he studies until late every day, his grades are not necessarily better than those of classmates who go to bed early.

Expensive things are not necessarily good quality; the cheap shoes I bought last time lasted three years without breaking.

The doctor said his illness doesn't necessarily require surgery; let's try medication and observation for a while first.

Friends you meet online are not necessarily unreliable; my husband and I met in a forum, and we've been married for five years now.