ought to与should意思接近,大多数情况下二者可以互换,但是should谈的是自己的主观看法,ought to则更多反映客观情况,在谈到法律、义务和规定时使用.
如：We should／ought to help each other and learn from each other in our work．
She is your mother,so you ought to support her．
We ought to go and see Mary tomorrow,but I don’t think we will．
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一、ought to具体用法如下：
1.(表示义务、责任等) 应当,应该
You ought to work harder than that.
2.(表示劝告、建议等) 应该,该
You don't look well.You ought to go to see the doctor.
3.(表示猜测、期望) 总应该,理应
It ought to be a fine day tomorrow morning.
4.“ought to + have + 过去分词”表示过去应做某事而实际未做
You ought to have told me that (but you didn't).
这时ought to和should可以互换使用.
二、ought to的否定式和疑问式
1.ought to的否定形式是ought后直接加not构成,其否定形式可缩写为oughtn't.
One ought not (oughtn't) to cross the street against the red light.
2.ought to的疑问式是将ought提到句首构成.
—Ought we to do it at once?—Yes,you ought to.
在反意疑问句里,下面两种形式都可以：
He ought to be here now,shouldn't (oughtn't) he?