① should用作助動詞,為shall的過去式,用來構成過去將來時,主要用于賓語從句中的第一人稱。
I told her that I should see her the next day. 我告訴她我將在第二天見她。
We thought we should never come here again. 我們原以為永遠也不會再到這里來了。
② should作情態(tài)動詞,表示“應該,應當”,通用于各種人稱。
We should help each other. 我們應該相互幫助。
You should write a letter to her. 你應該給她寫一封信。
Theory should be combined with practice. 理論應同實踐相結合。
③ should用于第一人稱,表示委婉語氣,為客氣、禮貌的說法。
I should say you'd better learn another foreign language. 我倒覺得你最好再學一門外語。
We should like to do the experiment right now. 我們倒是想立即做這項實驗。
④ should可用于特殊疑問句中,表示意外、驚奇、不能理解等,有“竟會,竟然會,怎么會”等義。
How should I know?我怎么會知道呢?
Why should I do it?為什么要我做那件事呢?
A:Go and cut down the tree. 去把那棵樹砍掉。
B:Why should I?為什么(要)我砍呢?
⑤ should be doing sth.表示應該在做什么。
You shouldn't be sitting here doing nothing. 你不應該坐在這里什么也不干。
You shouldn't be staying up so late. 你不該睡這么晚。
⑥ should have done sth.表示該做而實際未做,含有責備、遺憾、建議、指正的意味,意為“本應該”。
You should have come earlier. 你本該早些來的。
These manuscripts should have been kept in a dry place. 這些手稿本應存放在干燥的地方。
You should have told him you don't like to do it. 你來應告訴他你不喜歡做那件事的。
There is no reason why he should have sold the house. 他竟然把房子賣了,簡直毫無理由。
⑦ shouldn't have done sth.表示不該做卻做了,或該做卻沒做,含有責備等意味。
This kind of flower should not have been watered so often. 這種花本不該澆水這樣勤的。
She shouldn't have left home without a word. 她不該什么也沒說就離開了家。
You shouldn't have told her the news. 你本不該把消息告訴她的。(但卻告訴了)
You should have told her the news. 你本該把消息告訴她的。(但卻沒告訴)
⑧ should用在虛擬語氣中,相當于would。
If we had planted this kind of trees in a damp place,they should have grown better. 這種樹要是種在潮濕的地方,會長得更好。
If I were to do the job,I should do it in a different way. 要是我來做這項工作,我會以不同的方式做。