adverb, verb, noun, punctuation, pronoun · surely, certainly, necessarily, or expressing a requirement (must)

你明天一定要来参加会议。

adjective, adverb · to a certain extent, degree, or level; some amount of

这篇文章在一定程度上反映了现实。

adjective · fixed, specified, given, or particular

这里的规矩是一定的，不能随意更改。