说明

must 偏主观（自己觉得必须），have to 偏客观（外部条件要求），否定形式意思差别很大：mustn't 是禁止，don't have to 是不必。

同类条目

• 主谓一致：就近原则 —— Either you or he is right.
• 现在完成时 vs 一般过去时 —— I have lived here for 5 years. / I lived there in 2010.
• 定语从句：that 与 which —— The book that/which I bought is good.
• 虚拟语气：if 条件句 —— If I were you, I would take it.
• 非谓语：doing 与 to do —— I enjoy reading. / I want to go.
• 倒装：否定词提前 —— Never have I seen such a thing.
• 比较级：as ... as 与 than —— He is as tall as I am. / He is taller than I am.
• 情态动词表推测 —— It must be true. / It can't be true.