What is desired or ideal. We use ought to when talking about things which are desired or ideal:
They ought to have more parks in the city centre.
We ought to eat lots of fruit and vegetables every day.
We use ought to have + V3 form to talk about things that were desired or ideal in the past but which didn’t happen. It can express regret:
We ought to have locked the gate. Then the dog wouldn’t have got out. (The ideal or desired thing was that we locked the gate, but we didn’t.)
I often think that I ought to have studied medicine not pharmacy. (I would be happier now if I had studied medicine.)
USES2¶
What is likely. We can use ought to when we talk about what is likely or probable:
The concert ought to only take about two hours so we’ll be home by 12 pm.
There ought to be some good films at the cinema this weekend.
THE NEGATIVE¶
The negative is formed by adding ‘not’ after ought (ought not to). It can be contracted to oughtn’t to. The negative of ought to is not common. We usually use shouldn’t or should not instead.
OUGHT TO OR SHOULD?¶
Ought to and should are similar in meaning. Should is more common than ought to. Ought to is more formal than should: