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I can’t quite grasp the difference between sollen and müssen. They both express a duty, something that has to be done. In Italian, my native language, we just have one word for both, and so I can’t decide when I can only use one of them. In some uses, the two are equivalent, right? So, when is it right to use müssen and when sollen?
Could you explain the difference in connotation through examples?
According to its definition, sollen is used if something is not completely obligatory, but it would be really disadvantageous for somebody if the opposite happened, whereas müssen is really strict and utilized to determine rules and laws or if something is an inevitable condition for something else. Note that the opposite of müssen (a prohibition) is nicht dürfen, whereas nicht müssen means to not need to. Here are a few examples for which only müssen is applicable.
Sie müssen sich anmelden, bevor Sie die Forenbeiträge lesen können.
You have to log in before you can see the forum posts.Das Licht muss um 23 Uhr abgeschaltet werden.
The lights have to be switched off at 11 PM.Sie müssen mindestens 50 Punkte erreichen, um die Prüfung zu bestehen.
You have to score at least 50 credits to pass the exam.Sie dürfen diesen Bereich nicht betreten.
You must not enter this area.
Furthermore, müssen is used if somebody has to keep an appointment or perform an order they were given:
Morgen muss ich zum Zahnarzt.
I have to see a dentist tomorrowEr musste sein Zimmer aufräumen.
He had to tidy up his room.
An exception would be the Ten Commandments which are determined using sollen (e.g. Du sollst nicht stehlen) in German despite they are probably meant to be completely obligatory. I don‘t exactly know why, but determining compulsory rules with sollen has become unusual and sounds outdated, at least in written language, so nobody would write house rules or an employment contract with sollen.
However, there are lots of situations where both words can be used as synonyms, i. e. in spoken German, because sollen is considered a little more polite and often preferred if you give somebody an order or hint. To make it even more friendly, the subjunctive form sollte is often used.
Du solltest mehr schlafen, sonst kannst du dich nicht mehr konzentrieren.
You should sleep more, otherwise you won't be able to concentrate anymore.Du sollst doch nicht immer deine Hose schmutzig machen!
Didn't I tell you to not dirty your trousers every time? (Often, parents criticize their children like this)Der Staat sollte sich viel mehr um die Einwanderer kümmern.
The government should care way more for the immigrants.
You could use müssen resp. nicht dürfen in those three sentences as well, but it would sound way more harsh than sollen and indicate that the speaker is already really angry and/or uncomprehending about the way somebody else is behaving.
Müssen expresses general obligation. Sollen is an obligation given by someone. So when you use sollen, you do imply that someone told you so.
Ich muss gehen. I have to go (for whatever reason).
Ich soll gehen.
I have (just) been told to go.
Common contexts for sollen are doctors orders as well as the ten commandments.
Note that the the situation is different for sollte and müsste.
Müssen is quite more narrow in it's use:
Ich muss noch aufräumen. (I have to tidy up.)
This is a duty/necessity given to me by someone else or myself. I think that I have to fulfill it.
Ich muss den Kaffee ohne Milch trinken. (I have to drink coffee without milk.)
There is no milk left, so I have to drink coffee without milk. This is due to external circumstances.
Das muss Fred sein. (This has to be Fred.)
As I was expecting Fred, I reason that it is him.
When using „müssen“ as perfect auxiliary, this use remains as only option:
Die Strasse ist nass, es muss geregnet haben. (The street is wet, it must have rained.)
I reason that it must have rained as the street is wet.
Sollen is far wider. It is difficult to grasp, as there are many uses.
Ich soll mein Zimmer aufräumen.
I have to tidy up my room, but it is not as strict as „müssen“.
In Jerusalem soll sich mein Schicksal entscheiden. (My fate will be decided in Jerusalem.)
„Soll“ serves as a replacement for „werden“ (Futur) here. It can be used to talk about things that are supposed to happen in the future.
Dein Wille soll geschehen!
Here, it serves as a replacement for optative mood, which is usually conveyed by Konjunktiv I.
Er soll trinken. (He should drink or I've heard that he drinks.)
„Sollen“ is often used to voice out assumptions. This meaning is left when used as perfect auxiliary:
Er soll getrunken haben (I've heard/I assume that he drank.)
I think that „sollen“ is the most difficult modal verb.
Right. Romance or Latin languages do not distinguish between sollen und müssen. [Amazingly, automatic translators like Google-translate or Babelfish have big problems with it (presently).] The general rule is that:
Ich soll aufräumen. Er soll etwas mitbringen. Du sollst still sein. Wir sollen morgen wiederkommen.
Das muss gemacht werden. Da muss er durch. Da muss man mitmachen. Du musst es ihm sagen.
As you reference Italian (ciao!), I guess you would translate by dovere. You might think of sollen as the conditional (dovresti) and müssen as the direct correspondence (devi ballare). But both modal verbs exist in conditional form (Konjunktiv): ich sollte gehen, ich müsste schlafen. And there the easy rule goes …
Better think of
to start with.
To add to the other answers: "sollen" whenever in laws always has the meaning of "müssen" - there are "Soll-Bestimmungen" (which are compulsory) which are opposed to "Kann-Bestimmungen" (which are optional).
I suppose this is derived from some older use of the word, as is also reflected in the ten commandments (as mentioned elsewhere).
I tend to consider müssen/must like something that must be done no matter what. It's a rule. You must wash your hands, otherwise you can't touch the food.
Sollen/shall is what your doctor will tell you: you shall stop smoking if you want to live. You shall undergo surgery. It's a prescription. It isn't something that must be done, it's something that it's up to you but it's simply the only way. That's why, I think, it's called "moral obligation".
Edit: well, hope this helps.
It seems a key source of misunderstanding for English speakers is translating müssen into must. Better translations of this verb are "to have to" or "to need to"
Eg Ich muss = I have to, I need to Ich muss nicht = I don't have to, I don't need to (not "I must not")
Müssen is an obligation.
Sollen express something you have to do but it is an order or a suggestion from someone else!
