können and müssen

1.können and müssen

können and müssen are two central modal verbs. They usually do not name the action themselves: they show how the subject relates to another verb’s action.

In a main clause the modal is conjugated; the main verb stays in the infinitive and usually stands at the end:

2.The core contrast

The same action changes meaning only because of the modal:

The first means coming today is possible. The second means coming today is necessary. The infinitive kommen stays the same.

3.Forms of können in Präsens

In the singular the vowel changes: können → kann / kannst. The forms for ich and er/sie/es match.

4.Forms of müssen in Präsens

müssen follows a similar pattern: the umlaut disappears in the singular. Again ich and er/sie/es match.

5.The special singular pattern

These forms are not built like regular lernen (ich lerne / er lernt). With können and müssen, ich has no ordinary -e, and er/sie/es has no ordinary -t: ich kann / er kann, ich muss / er muss.

At A1 it is practical to memorize these small paradigms as ready-made sets.

6.können: ability

A frequent use is to say that someone has a skill:

7.können: practical possibility

können can also mean that the situation allows an action — not necessarily a learned skill:

Permission is a different idea; that is dürfen.

8.müssen: necessity

müssen says that an action is necessary. The source can vary: a rule, a deadline, a plan, or the situation.

9.One action — two meanings

The second verb names the action; the modal supplies the modality.

10.The verbal bracket

In a statement the finite modal stands in position 2 and the infinitive at the end. The middle holds the rest of the information.

11.Starting with time or place

If time or place comes first, the modal still stands in position 2 and the subject follows it. The infinitive stays at the end.

12.Yes/no questions

In a yes/no question the finite modal comes first.

13.W-questions

The W-word comes first, the modal follows it, and the infinitive stands at the end.

14.Negation: nicht können

nicht können means the action is impossible or the person is not able to do it.

15.Negation: nicht müssen

nicht müssen means “not necessary / not required”. It is not a prohibition.

Du musst heute nicht kommen. — coming is not required. Prohibition is nicht dürfen.

16.Two verbs in the pattern

The basic construction is finite modal + infinitive of the main verb. The modal carries person and number; the second verb is not conjugated.

Do not conjugate both: not Ich kann schwimme, but Ich kann schwimmen..

17.When the second verb is left out

If the action is clear from context, the second verb is sometimes omitted: Ich kann das., Ich muss nach Hause.. The central A1 model remains “modal + … + infinitive”.

18.Typical mistakes

Incorrect: Ich könne schwimmen.. Correct: Ich kann schwimmen..

Du musst nicht kommen means “you don’t have to come”, not “you are not allowed to come”.