Keywords:should not (shouldn't),
ought not (oughtn't),
must not (mustn't)
1. Used alone to mean you think that the action under discussion is not right, it is not good that it happens, or that you feel that it will not happen.
1. Used before or after a verb (action) sign to mean that you think that it is not right or not good that the action happens, or that you feel that it will not happen. English = shouldn't, ought not to.
2. You use this sign when you are suggesting that someone not do something.