Learn Hardcore German: Der Vater musste sich sofort ausziehen, weil sein Hemd dreckig geworden ist. - The father had to undress immediately because his shirt got dirty.

In German, many verbs require a reflexive pronoun even if the action clearly affects the subject. In this case, “ausziehen” is a reflexive verb meaning “to undress oneself.” Therefore, “sich” is needed to show that the father is the one performing the action on himself.

How does “musste” function in this sentence?

“Musste” is the simple past (Präteritum) form of the modal verb “müssen,” which expresses necessity or obligation. Here it indicates that the father had to undress immediately, placing the obligation in the past.

Why does the separable verb “ausziehen” appear in its complete infinitive form rather than being split?

When a modal verb is used in a sentence, the main verb—in this case “ausziehen”—remains in its infinitive form and is positioned at the end of the clause. Unlike a standard sentence with a separable verb where the prefix might be detached and placed at the end, the modal construction keeps “ausziehen” intact.

What is the role and structure of the subordinate clause starting with “weil”?

The word “weil” introduces a subordinate (causal) clause that explains the reason for the action in the main clause. In German subordinate clauses, the finite verb is placed at the end, which is why “ist” appears as the last word in “weil sein Hemd dreckig geworden ist.”

Why is the present perfect tense (“geworden ist”) used in the subordinate clause instead of the simple past?

In colloquial spoken German, the present perfect is commonly used to describe past events, even in subordinate clauses. “Sein Hemd dreckig geworden ist” uses the auxiliary “ist” together with the past participle “geworden” to indicate that the shirt became dirty. This formation emphasizes the change of state and is typically preferred in everyday communication over the simple past form.