adjective, noun · hard, strong, or firm in physical or abstract structure

这种胶水粘得不固，东西很容易掉。

conjunction · indeed, of course, or granted (often used to acknowledge a point before a contrast)

学外语固非易事，但很有趣。

adjective · surely, assuredly, or undoubtedly

固所愿也，不敢请耳。