Differences between sollen and müssen
The modal verb müssen expresses a necessity in general, while sollen expresses a necessity that is the result of a request/command addressed to the subject of the verb.
| Examples | ||
| Paul soll morgen Überstunden machen. | a. because his boss has asked him to. |
necessity (request/command)
|
| Paul muss morgen Überstunden machen. | b. because he wants to finish his project. |
necessity
|
| c. because he needs money. |
necessity
|
|
| d. because he was sick today. |
necessity
|
This means that müssen contains the meaning of sollen, it is, however, not clear that it involves a request/command. If the aspect of "request/command" is important to what is being said, it has to be clarified by the context.
| Examples | ||
| Paul muss morgen Überstunden machen, weil das sein Chef von ihm verlangt hat. |
=
|
Paul soll morgen Überstunden machen. |
If what is being said contains the aspect of request/command, according to context, sollen can be replaced by müssen.
There is also a difference in the intensity of the necessity. Müssen expresses a strong necessity that cannot be overlooked without consequences.
| Example | meaning | intensity of necessity |
| Du sollst einkaufen gehen! | Du wirst von mir/uns/jdm. aufgefordert, einkaufen zu gehen. | + |
| Du musst einkaufen gehen! | Du hast keine Wahl. Wenn du es nicht tust, gibt es Folgen. | + + |