needn't 是情态动词,表示不必要,没义务做某事, 后面直接加bare infinitive,无to的动词不定式,即动词原形, 等同don't have to. 反义词是 must 有义务做某事。疑问句时,不需加助动词,如 Need I work late tonight? 我需要加班吗?
No ,you needn't, but you must tomorrow 不,不需要。但明天必须要。用need提问,表示需要听到对方否定回答,如needn't. 对过去的评价是needn't 现在完成时you needn't have said that.你当时没必要那么说。而need 是普通动词,表示需要:否定、疑问...