情态动词

简单情态动词总结（专升本）情态动词（Modal verb）本身有一定的词义，表示语气的单词。但是不能独立作谓语，只能和动词原形一起构成谓语。情态动词用在行为动词前，表示说话人对这一动作或状态的看法或主观设想。

情态动词

• 含义
  • may于句首+主语，表祝愿
  • may/might as well最好，还是
  • must必须 mustn`t禁止
  • should应该shouldn`t不应该 should=ought to
• 推测
  • cann`t不可能 can用于否定句疑问句中
  • must一定是
• 十have done表推测
  • must have done过去一定做sth
  • can`t/couldn`t have done过去不可能已经做sth
  • may/might have done过去可能做sth
  • may/might not have done过去可能没做sth
• +have done表虚拟
  • should/ought to have done过去本应该做某事却未做 shouldn`t/oughtn`t to have done过去本不该做某事却做了
  • need have done过去本有必要做却未做 needn`t have done过去本没必做却做了，
  • could（不可用can）have done过去本能够做某事却未做 couldn`t have done过去本不能够做某事却做了，过去不可能做某事
  • might（不可用may）have done 过去本可能做某事却未做
• 主题
  • used to do sth过去经常做某事 be used to doing sth现在经常做某事 had better do sth=may as well do sth最好做某事 would rather do sth 宁愿做某事would rather do……than do宁愿 ……而不愿
• must提问，
  • 肯must
  • 否needn`t/don`t have to