Differences between modal verbs (müssen vs sollen, dürfen vs können) — (müssen = must/have to vs sollen = should/ought to / supposed to; dürfen = may/be allowed to vs können = can/be able to)

• müssen = must / have to: obligation or necessity (also logical deduction). Example: "Ich muss arbeiten." (I have to work.)
• sollen = should / be supposed to: advice, moral duty, instruction from someone else, or reported information. Example: "Du sollst deine Hausaufgaben machen." (You should / are supposed to do your homework.)
• dürfen = may / be allowed to: permission (negated = prohibition). Example: "Darf ich reinkommen?" (May I come in?)
• können = can / be able to: ability or possibility (sometimes used to make informal requests). Example: "Ich kann schwimmen." (I can swim.)

• Primary meaning: necessity or obligation (internal or circumstance-based). It expresses that something is required.
• Example: "Ich muss morgen früh aufstehen." (I have to get up early tomorrow.)
• Example: "Wir müssen jetzt gehen, sonst verpassen wir den Bus." (We must leave now, otherwise we'll miss the bus.)
• Another common use: logical deduction. In this sense it equals English "must" as a conclusion.
• Example: "Er hat Fieber. Er muss krank sein." (He has a fever. He must be sick.)

• Primary meanings:
• Advice or recommendation (English "should"). Example: "Du solltest mehr schlafen." (You should sleep more.)
• An instruction coming from someone else (external obligation): "Der Lehrer sagt, ihr sollt leise sein." (The teacher says you should be quiet / you are to be quiet.)
• Reported information or rumor: "Er soll nach Berlin fahren." (He is said to be going to Berlin / he is supposed to go to Berlin.)

• Main meaning: permission (may / allowed to). Use it when someone is allowed or not allowed to do something.
• Example: "Darf ich kurz telefonieren?" (May I make a quick call?)
• "Du darfst hier nicht parken." (You are not allowed to park here.)
• Past: "durfte" = was allowed to / had permission. Example: "Als Kind durfte ich länger aufbleiben." (As a child I was allowed to stay up later.)

• Main meanings:
• Ability / capability: "Ich kann schwimmen." (I can swim / I am able to swim.)
• Possibility: "Es kann morgen regnen." (It could/may rain tomorrow.)
• Informal requests/offers: "Kannst du mir helfen?" (Can you help me?) — often polite but less formal than Konjunktiv II (Könnten Sie...).
• Past: "konnte" = could / was able to. Example: "Ich konnte gestern nicht kommen." (I couldn’t come yesterday.)

• müssen: ich muss, du musst, er/sie/es muss, wir müssen, ihr müsst, sie/Sie müssen
• sollen: ich soll, du sollst, er/sie/es soll, wir sollen, ihr sollt, sie/Sie sollen
• dürfen: ich darf, du darfst, er/sie/es darf, wir dürfen, ihr dürft, sie/Sie dürfen
• können: ich kann, du kannst, er/sie/es kann, wir können, ihr könnt, sie/Sie können

• musste (müssen), sollte (sollen), durfte (dürfen), konnte (können)
• Example: "Gestern musste ich arbeiten." (Yesterday I had to work.)
• "Früher durfte ich länger wach bleiben." (Back then I was allowed to stay up later.)

• Examples:
• "Ich habe gestern länger arbeiten müssen." (I had to work longer yesterday.)
• "Er hat das nicht machen dürfen." (He was not allowed to do that.)
• "Wir haben dir nicht helfen können." (We couldn’t help you.)
• "Sie hat das tun sollen." (She was supposed to do that / she should have done that.)

• Main clause (statement): modal verb is conjugated and in second position; the main verb (infinitive) goes to the end.
• "Ich muss jetzt gehen." (I have to go now.) — "muss" in 2nd position, "gehen" at the end.
• Subordinate clause (with dass, weil, etc.): the modal (finite) goes to the end, after the main infinitive.
• "Ich denke, dass ich gehen muss." (I think that I must go.) — "gehen muss" at the end.
• Perfect with modal + main verb: both infinitives go to the end.
• "Er hat früher länger arbeiten müssen." (He had to work longer before.)

• Confusing müssen and sollen:
• Wrong: Translating English "should" always as "müssen." Correct: use "sollen/solltest" for "should."
• Wrong: "Du musst deine Mutter anrufen." (if you mean "you should call your mother").
• Better: "Du solltest deine Mutter anrufen." (You should call your mother.)
• Confusing können and dürfen (ability vs permission):
• "Ich kann nicht kommen" (I can’t come = I’m unable) vs "Ich darf nicht kommen" (I’m not allowed to come).
• Using present perfect incorrectly with modals:
• Wrong: "Ich habe muss gearbeitet." Correct: "Ich habe arbeiten müssen." (I had to work.)
• Interpreting "sollen" as a logical conclusion:
• "Er soll krank sein" = He is said to be ill (reported), not "He must be ill" (that would be "Er muss krank sein").

• If the obligation comes from outside (someone told you), try "sollen." If it’s a necessity you feel or that comes from circumstances, use "müssen."
• To ask for permission use "Darf ich...?" In casual spoken German "Kann ich...?" is common but less precise.
• For polite requests use Konjunktiv II: "Könnten Sie mir bitte helfen?" rather than present "Können Sie..." in formal situations.
• Remember the double infinitive pattern in perfect tense: "haben + main-infinitive + modal-infinitive." Practice by making a few sentences in the past tense.

Obligation / necessity (müssen)

• "Ich muss jeden Tag zur Arbeit." (I have to go to work every day.)


• "Wir müssen die Regeln befolgen." (We must follow the rules.)


• "Ich musste gestern länger bleiben." (I had to stay longer yesterday.)


• "Du musst nicht kommen, wenn du keine Zeit hast." (You don’t have to come if you don’t have time.)

Advice, instruction, or reported obligation (sollen)

• "Du sollst das nicht tun." (You should not do that / you are not supposed to do that.)


• "Der Arzt sagt, ich soll mich ausruhen." (The doctor says I should rest.)


• "Ihr sollt leise sein." (You are to be quiet — instruction.)


• "Sie sollen verheiratet sein." (They are said to be married — reported information.)


• "Ich sollte gestern früher ins Bett gehen." (I should have gone to bed earlier / literal past of advice.)

Permission and prohibition (dürfen)

• "Darf ich hier parken?" (May I park here?)


• "Die Kinder dürfen bis zehn Uhr fernsehen." (The children are allowed to watch TV until ten o’clock.)


• "Du darfst das nicht nehmen." (You are not allowed to take that.)


• Past: "Früher durfte ich nicht so lange aufbleiben." (I wasn’t allowed to stay up so late earlier.)

Ability and possibility (können)

• "Kannst du Gitarre spielen?" (Can you play the guitar?)


• "Ich kann drei Minuten unter Wasser bleiben." (I can stay under water for three minutes.)


• "Es kann sein, dass er zu spät kommt." (It may be that he will come late / He might be late.)


• Past: "Ich konnte gestern nicht teilnehmen." (I couldn’t participate yesterday.)

• A verb that modifies the meaning of another verb to express necessity, permission, ability, request, or obligation (e.g., müssen, sollen, dürfen, können).

• The base form of a verb (e.g., gehen, arbeiten, helfen). With modals, the infinitive often moves to the end of the clause.

• In the perfect tense, when a modal is used with another verb, German commonly uses "haben + main-infinitive + modal-infinitive" (e.g., "Ich habe arbeiten müssen").

Final quick reference (one-line cheats)

• müssen = must / have to (obligation, also logical deduction)


• sollen = should / be supposed to (advice, instruction from others, reported speech)


• dürfen = may / be allowed to (permission / prohibition when negated)


• können = can / be able to (ability, possibility; informal requests)