Should, ought to, must
Should and ought have similar meanings. They are both used to talk about obligation, and to give advice or instructions.
- We should respect our parents.
- We ought to respect our parents.
- You should stop smoking.
- You ought to stop smoking.
Must is stronger than should and ought.
- You must stop smoking. (A command.)
- You should/ought to stop smoking. (A piece of advice.)
Must expresses certainty. Should/ought to expresses probability.
- He must be home now. (It is certain.)
- He should be home now. (It is probable.)
Modal Auxiliary Verbs
May and Can: differences
Should: other uses
Must and have to: The Difference
Should, Ought and Must: The difference