als vs wenn vs wann | German Grammar

English uses one little word, "when," for three quite different jobs: asking a question, marking a one-time past event, and marking a repeated or hypothetical situation. German splits these across three words — wann, als, and wenn — and using the wrong one is one of the most persistent errors English speakers make. This page gives you a clean decision tree and shows you exactly where the trap lies.

The decision tree

Ask yourself, in order:

Step	Question	Use
1	Is it a question (direct or indirect)?	wann
2	A single, completed event in the past?	als
3	Repeated past ("whenever"), present, future, or a condition ("if")?	wenn

All three are lowercase, and all three send the conjugated verb to the end of the clause — wann and wenn and als are subordinating words, so word order is verb-final.

wann — the question word

Use wann whenever you are asking about time, whether the question is direct or buried inside another sentence (an indirect question). The English clue: you could answer it with a specific time.

Wann kommst du heute Abend nach Hause?

When are you coming home tonight?

Ich weiß nicht, wann der Zug abfährt.

I don't know when the train leaves. (indirect question)

Kannst du mir sagen, wann der Film anfängt?

Can you tell me when the film starts? (indirect question)

The key insight: wann is the only one of the three that is a question word. If you can rephrase the clause as a real question — "At what time?" — it is wann, even when it is embedded in a statement like Ich weiß nicht, wann….

als — one completed event in the past

Use als for a single, finished event or period in the past — something that happened once. This is "when" in the sense of "on that one occasion" or "at the time that."

Als ich gestern ankam, war niemand zu Hause.

When I arrived yesterday, no one was home.

Als ich ein Kind war, haben wir jeden Sommer am Meer verbracht.

When I was a child, we spent every summer at the sea.

Als der Krieg zu Ende war, kehrten viele Menschen in ihre Heimat zurück.

When the war ended, many people returned to their homeland.

Notice that Als ich ein Kind war refers to one continuous, bounded stretch of the past — your childhood, viewed as a single span — so it is als even though many summers happened inside it. The clause itself ("being a child") is one completed past situation.

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A useful test for als: if you could say "back then," "on that occasion," or "at the time" in English, you want als. It points to a specific, non-repeating moment or period that is now over.

wenn — repeated past, present, future, and conditions

Use wenn in three situations:

(a) Repeated or habitual past — "whenever." Often reinforced with immer wenn or jedes Mal, wenn.

Immer wenn es regnete, blieben wir drinnen und spielten Karten.

Whenever it rained, we stayed inside and played cards.

Jedes Mal, wenn ich ihn besuchte, kochte er etwas Italienisches.

Every time I visited him, he cooked something Italian.

(b) Present and future time — "when."

Wenn ich nach Hause komme, rufe ich dich sofort an.

When I get home, I'll call you right away.

Wenn du in Berlin bist, müssen wir uns unbedingt treffen.

When you're in Berlin, we absolutely have to meet up.

(c) Condition — "if." German uses the same wenn for "if," because conditions and future-time clauses are closely related.

Wenn du Zeit hast, können wir morgen ins Kino gehen.

If you have time, we can go to the cinema tomorrow.

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The cleanest way to keep wenn straight: it covers everything except questions and single past events. Repeated past, anything present or future, and any condition all funnel into wenn. That is why German speakers describe it as the "if/whenever" word.

The hard part: als vs wenn in the past

This is the distinction English gives you no signal for, and it is where almost all the errors happen. In the past tense, German forces you to decide whether the event happened once (als) or repeatedly (wenn). English says "when" for both.

Als ich ankam, regnete es.

When I arrived, it was raining. (one specific arrival — als)

Wenn ich ankam, regnete es.

Whenever I arrived, it was raining. (each time I arrived — wenn)

These two sentences are spelled almost identically in English ("when I arrived") but mean different things, and only German makes the difference explicit. Als ich ankam is a single arrival; Wenn ich ankam is a recurring pattern. Before you write a past-time "when" clause, pause and ask: once, or every time?

A side note: the other als

Be aware that als has a second, unrelated job: it is the comparison particle after a comparative ("than"). That is a different word doing a different job, but it shares the spelling.

Mein Bruder ist größer als ich.

My brother is taller than I am. (als = than, comparison — not temporal)

Don't let this confuse the temporal decision; if you are translating "than," it is comparison-als and the rules above do not apply.

Common Mistakes

1. Using wenn for a single past event. The big one — English "when" pushes learners toward wenn, but a one-time past event needs als.

❌ Wenn ich gestern ankam, war niemand da.

Incorrect — a single past arrival requires als, not wenn.

✅ Als ich gestern ankam, war niemand da.

When I arrived yesterday, no one was there.

2. Using wann as a conjunction in a statement. Wann is for questions only; a statement about a single past event takes als.

❌ Ich erinnere mich an den Tag, wann wir uns kennenlernten.

Incorrect — this is not a question, so use als.

✅ Ich erinnere mich an den Tag, als wir uns kennenlernten.

I remember the day when we met.

3. Using als for a repeated past event. "Whenever / every time" in the past is wenn, not als.

❌ Als ich klein war, las mir mein Vater jeden Abend vor.

Acceptable only if you mean childhood as one span; for the repeated bedtime reading itself, use immer wenn.

✅ Immer wenn ich Angst hatte, las mir mein Vater eine Geschichte vor.

Whenever I was scared, my father read me a story.

4. Using als or wenn in an indirect question. Embedded questions still need wann.

❌ Ich frage mich, wenn der Bus endlich kommt.

Incorrect — this is an indirect question, so use wann (and it changes the meaning to a condition otherwise).

✅ Ich frage mich, wann der Bus endlich kommt.

I wonder when the bus is finally coming.

Key Takeaways

wann = question word, direct or indirect (Wann…? / Ich weiß nicht, wann…).
als = a single, completed event or bounded period in the past (Als ich ankam…).
wenn = repeated past ("whenever," often immer wenn), all present/future time, and conditions ("if").
The hardest contrast is past-time als (once) vs wenn (every time) — a distinction English does not mark, so always ask "once, or each time?"
All three are lowercase and send the verb to the end of the clause; watch out for the unrelated comparison particle als meaning "than."

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