情態助動詞

助動詞	用法	現在式 / 未來式	過去式
may	禮貌請求 (只與I或see連用)	May I borrow your pen?
	正式的許可	You may leave the room
	對事情看法不是很肯定的狀況	Where is John? He may be at the library?	He may have been at the library.
might	禮貌請求(少用)	Might I borrow your pen?
	不是很肯定狀況下	Where is John? He may be at the library?	He may have been at the library.
should	表示對事情的期待	I should study tonight.	I should have studied last night, but I didn’t.
	對事情看法接近肯定的狀況	She should do well on the test tomorrow.	She should have done well on the test.
ought to	表示對事情的期待	I ought to study tonight.	I ought to have studied last night, but I didn’t.
	對事情看法接近肯定的狀況	She ought to do well on the test tomorrow.	She ought to have done well on the test.
had better	強烈要求	You had better be on time, or we will leave without you.
be supposed to	預期	Class is supposed to begin at 10:00.
	未完成的預期		Class was supposed to begin at 10:00, but it began at 10:15.
must	語氣強烈的必須	I must go to class today.	I had to go to class yesterday. *用had to
	禁止(否定式)	You must not open that door.
	對事情看法接近肯定的狀況	Mary isn’t in class. She must be sick.	Mary must have been sick yesterday.
have to	語氣普通的必須	I have to go to class today.	I had to go to class yesterday.
	不必(否定式)	I don’t have to go to class today.	I didn’t have to go to class yesterday.
have got to	用在口語的必須	I have got to go to class today.	I didn’t have to go to class yesterday.
will	絕對確定的事情	He will be here at 6:00.
	意願	The phone is ringing. I will get it.
	禮貌請求	Will you please help me?
be going to	絕對發生的預測	He is going to be here at 6:00.
	明確的計畫	I am going to paint my bedroom.
	未完成的意圖或計畫		I was going to paint my room, but I didn’t have time.
can	能力 / 可能性	I can run fast.	I could run fast when I was a child, but now I can’t.
	非正式的許可	You can use my car tomorrow.
	非正式的禮貌請求	Can I borrow your pen?
	不可能(否定句)	That can’t be true!	That can’t have been true!
could	過去的能力		I could run fast when I was a child.
	禮貌的請求	Could I borrow your pen? Could you help me?
	建議(肯定句)	I need help in math. You could talk to your teacher.	You could have talked to your teacher.
	對事情看法不是很肯定的狀況	Where’s John? He could be at home.	He could have been at home.
	不可能(否定句)	That couldn’t be true!	That couldn’t have been true!
be able to	能力	I am able to help you. I will be able to help you.	I was able to help him.
would	禮貌的請求	Would you please help me? Would you mind if I left early?
	寧願	I would rather go to the park than stay home.	I would rather have gone to the park.
	過去反覆發生的動作		When I was a child, I would visit my grandparents every weekend.
	禮貌的「想要」 (與like連用)	I would like an apple, please.
	未實現的願望		I would have liked a cookie, but there were none in the house.
used to	過去反覆發生的動作		I used to visit my grandparents every weekend.
	只存在於過去的事情		I used to live in Spain. Now I live in Korea.
shall	禮貌的建議問句	Shall I open the window?
	以I 或we為主詞的未來式	I shall arrive at nine.