The modal verbs of English are a small class of auxiliary verbs used mostly to express modality (properties such as possibility, obligation, etc.). They can be distinguished from other verbs by their defectiveness (they do not have participle or infinitive forms) and by the fact that they do not take the ending -(e)s in the third-person singular.
近义、反义、联想词
解析
have to 通俗用语,指受客观条件或环境迫使而“不得不”做某事,突出客观性。 must 通常表示命令或说话人主观认为必须要做某事,含强调语气,侧重主观性。