专四情态动词

专四情态动词的思维导图，整理了情态动词+do、情态动词+have done、情态动词、用作(含有)情态动词的短语，一起来学习。

情态动词

情态动词+do

对现在或将来事实的猜测

情态动词+have done

对过去事实的猜测

must+have done

过去一定做过某事

否定：can't/couldn't have done

can/could+have done

过去本能够做而未做，表遗憾和惋惜

may/might+have done

过去可能已做了某事，表一种不太有把握的推测

should/ought to+have done

本应该做而实际没有做，含责备或遗憾的语气

否定：shouldn't/oughtn't to+have done

needn't+have done

没必要做而实际上做了

will/would+have done

情态动词

must

表命令，“必须”

Must I...——Yes, you must（No, you don't have to/needn't）

must 与 have to 的 区别

表推测，“一定”

need

情态动词，“必要”+do

实义动词，“需要”+to do

need doing=need to be done

can/could

表能力，“能够”

can/could 与 be able to的区别

表请求和允许

Can I use your dictionary——Yes, you can.(No, you can't)/ (No, I'm afraid not.)

表推测

could 比 can 语气更委婉

may/might

表祝愿，用于祈使句

May you succeed!

表请求和允许

May/Might I...——Yes, you can（No,you can't/mustn't）

表推测

might表示的可能性比may小

should/ought to

表劝告、建议和命令

should：应该

ought to：表义务或责任，比 should 语气重

表推测

should/ought to：客观推测

must：主观推测

will/would

表意志、愿望和决心

表请求和建议

表推测

shall

用于第一人称，征求对方的意见

用于一、三人称，征求对方的意见或向对方请示

用于二、三人称，说话人给对方的命令、警告、允诺或威胁；义务或规定（法律文件中）

dare

情态动词，“敢”+（not）do

实义动词，“敢”+to do

用作(含有)情态动词的短语

used to+do

否定：used not to (usedn't to)

疑问：Didn't+主+use to...?=Usedn't+主+to...（used提到主语前，或用did引起）

had better+do（用于现在时或一般将来时，所有人称都适用）

否定：had better not

疑问：Had+主+better...

would rather+do

其他：would rather(sooner)+do+than+do

had rather（用法同would rather）

cannot (help) but+do 不能不，必须，只好

cannot afford +to do

cannot(couldn't)help+doing

may well+do 理应，有足够的理由

may(might) as well+do 还不如，不妨

e.g. You might as well throw your money into the sea as lend it to him.

cannot...too 无论如何...也不过分

e.g. We cannot recommend this book too strongly.这本书很好，无论我们如何推荐也不过分。

变体：couldn't/impossible/difficult...enough/sufficient/exaggerate,over-

e.g. You cannot take sufficient care.你要特别小心。

e.g. No man can have too many friends.朋友愈多愈好。

e.g. The importance of adequate preparation cannot be overemphasized.充分准备的重要性再怎么强调也不为过。

would

表示过去反复发生的动作或某种倾向

对比：used to 过去常常(现已无此习惯)