“Als” vs “wenn” vs “wann” — distinguishing temporal and conditional uses of “when”

Als vs wenn vs wann — When to use each for time or condition

German has three common words that translate to English when: als, wenn, and wann. They are not interchangeable. Choose between them depending on whether you are asking a question, talking about a single past event, talking about repeated events or conditions, or forming an indirect question. Below you will find clear rules, formation notes (word order), many examples in German, and common learner mistakes.

What do als, wenn and wann mean?

- als — used for a single event or a specific time period in the past (temporal: one-off past). Example: Als ich klein war... (When/As I was small... — referring to that past period).
- wenn — used for repeated events (whenever), general truths, future time (when = as soon as), and conditions (if). It can mean "if" in conditional sentences. Example: Wenn es regnet, bleiben wir zu Hause. (If/When it rains...)
- wann — used for direct and indirect questions about time (When?). Example (direct): Wann kommst du? (When are you coming?) Example (indirect): Ich weiß nicht, wann er kommt. (I don’t know when he will come.)

When do I use 'als' (simple rule)?

Use als for a single, completed time in the past or to describe a past period. Als is a subordinating conjunction: in the clause it introduces the finite verb goes to the end.

Examples (German → English):
- Als ich zehn Jahre alt war, bekam ich mein erstes Fahrrad.
(When I was ten years old, I got my first bicycle.)
- Als er in die Küche kam, war der Kuchen schon fertig.
(When he came into the kitchen, the cake was already done.)
- Ich rief sie an, als der Film begonnen hatte.
(I called her when the movie had already started.)
- Als die Mauer fiel, feierten die Menschen auf den Straßen.
(When the Wall fell, people celebrated in the streets.)
- Als Kind spielte ich oft draußen.
(When I was a child / As a child I often played outside.)

Note: als is also used in comparisons (größer als = larger than) and in fixed expressions like als ob (as if). That use is different from the temporal als.

When do I use 'wenn' (simple rule)?

Use wenn for:
- repeated events / habits ("whenever"),
- general truths and scientific facts,
- future time clauses ("when" meaning "as soon as"),
- conditional sentences ("if").

Wenn is a subordinating conjunction too: verb at the end of the clause it introduces.

Examples (German → English):
- Wenn ich Zeit habe, lese ich Bücher.
(When/Whenever I have time, I read books — repeated/habitual.)
- Wenn Wasser 100 °C erreicht, kocht es.
(When/If water reaches 100 °C, it boils — general truth.)
- Wenn er morgen kommt, geben wir ihm das Geschenk.
(If/When he comes tomorrow, we'll give him the present — future event or planned occasion.)
- Wenn du willst, können wir jetzt gehen.
(If you want, we can go now — conditional.)
- Wenn ich mehr Zeit hätte, würde ich mehr lesen.
(If I had more time, I would read more — hypothetical present.)
- Wenn du früher angerufen hättest, hätte ich dir geholfen.
(If you had called earlier, I would have helped you — counterfactual past.)

When do I use 'wann' (simple rule)?

Use wann for direct questions (Where is "when"?) and for indirect questions (I asked when ...). You do not use wann to introduce normal temporal clauses (use als/ wenn instead).

Examples — direct questions (verb goes second):
- Wann kommst du?
(When are you coming?)
- Wann fängt der Film an?
(When does the movie start?)

Examples — indirect questions (subordinate clause; verb goes to the end):
- Ich weiß nicht, wann er kommt.
(I don’t know when he will come.)
- Sie fragte mich, wann die Prüfung stattfindet.
(She asked me when the exam takes place.)

Important: Don’t use wann as a temporal conjunction. Wrong: "Ich rief ihn an, wann er ankam." Correct: "Ich rief ihn an, als er ankam."

Word order: what happens to the verb?

- Als / Wenn: both are subordinating conjunctions. In the clause they introduce, the finite verb moves to the end.
Example: Wenn ich Zeit habe, komme ich vorbei. / Als ich Zeit hatte, kam ich vorbei.

- Wann (direct question): the question word is first and the finite verb is second (standard question word order).
Example: Wann kommst du?

- Wann (indirect question): the clause behaves like any subordinate clause and the verb goes to the end.
Example: Er fragt, wann du kommst.

Comma and clause position

If the subordinate clause (starting with als or wenn or the indirect question with wann) comes first, put a comma before the main clause: "Wenn du Zeit hast, ruf mich an." If the main clause comes first, the comma still separates the clauses: "Ruf mich an, wenn du Zeit hast."

Common mistakes learners make (with corrections)

1) Using wann in a normal time clause (not a question)
- Wrong: Ich rief ihn an, wann er ankam.
- Correct: Ich rief ihn an, als er ankam.

2) Using als for future or repeated events
- Wrong: Als du morgen kommst, sagst du mir Bescheid.
- Correct: Wenn du morgen kommst, sag mir Bescheid.
(Als cannot be used for future events.)

3) Confusing wann and ob in indirect questions
- English: I asked whether/whether he would come.
- Wrong: Ich fragte, wann er kommt. (This asks "when", not "whether".)
- Correct (whether): Ich fragte, ob er kommt.
- Correct (when): Ich fragte, wann er kommt.

4) Using wenn for a single past event (common but avoid if you mean a single moment)
- Wrong (if you mean a single past moment): Wenn ich gestern ankam, ...
- Better / Correct: Als ich gestern ankam, ...

Note on nuance: "Als ich ein Kind war, spielte ich oft draußen." — Using als with a past period like "as a child" is normal; it describes a time-span during which many repeated actions occurred. The short rule remains useful: single past/time period → als; repeated/habitual/conditional/future → wenn; question → wann.

Quick comparison and practical cheatsheet

- Use wann for questions (direct and indirect):
"Wann beginnt der Test?" / "Ich weiß nicht, wann der Test beginnt."

- Use als for a one-time or specific time in the past (or a past period):
"Als ich ankam, war das Licht aus."

- Use wenn for repeated actions (Whenever), general truths, future time (when = as soon as), and conditions (if):
"Wenn ich Zeit habe, besuche ich dich." / "Wenn es regnet, bleiben wir drinnen." / "Wenn du morgen kommst, sagen wir es ihm."

Parallel English examples (to feel the difference)

- "When I arrived, the store was closed." → "Als ich ankam, war das Geschäft geschlossen." (single past event)
- "When I arrive home, I make tea." → "Wenn ich nach Hause komme, mache ich Tee." (habit / future whenever)
- "When will you arrive?" → "Wann wirst du ankommen?" (question)

Extra note: 'falls' vs 'wenn'

- Falls = in case (slightly more hypothetical). Example: "Falls es regnet, nimm einen Schirm mit." (In case it rains, take an umbrella.)
- Wenn = if / when. Both can be used for condition, but falls often suggests a more tentative or less likely condition.

Glossary — short, useful definitions

- subordinating conjunction: a word that introduces a subordinate clause and typically sends the verb to the end (e.g., als, wenn).
- subordinate clause: a part of the sentence that depends on the main clause and often cannot stand alone.
- direct question: a question asked directly; question word first, verb second (e.g., Wann kommst du?).
- indirect question: a clause that reports a question (e.g., Ich weiß nicht, wann er kommt.) — behaves like a subordinate clause.
- conditional clause: a clause that expresses an "if" condition (often introduced by wenn).

Summary — How to choose quickly

- Ask a question about time? Use "wann."
- Talk about one event (or a past period) in the past? Use "als."
- Talk about repeated actions, general truths, future "when/as soon as," or an "if" condition? Use "wenn."

If you remember these three simple checks (question / single past / repetition-or-condition), you will choose the correct word in most situations. Practice noticing whether English "when" is a question, a single past moment, or an if/repeated idea — then map it to wann, als, or wenn.