English Lover said:
what's the difference in meaning:
1. I don't have to go to work tomorrow , it is saturday.
2. You mustn't go to work, you're too ill.
what's the difference in meaning:
1. I don't have to go to work tomorrow. It is Saturday. <<
don't have to - no requirement - no obligation -
2. You mustn't go to work. You're too ill. <<
It is not at all a good idea to go to work because you are ill. When "must" is used negatively, it is done to say something is not allowed. We could call this "prohibition".
In your sentence "must" is used to express very strong advice. It really is not a good idea at all to go to work if you are ill. A family member, friend, or a doctor could be the speaker here. One of these people would be in a position to have some influence on the listener's actions. The speaker would not be indicating that going to work is prohibited, but would be suggesting in a very strong way that it is not a good idea - at all.
