wenn vs als vs wann — choosing between the three 'when's
English uses one word — when — for three different jobs. German splits them. wenn introduces a condition or a repeated/general/future situation: Wenn es regnet, bleibe ich zu Hause. = When it rains, I stay home. (always / generally) als introduces a one-time event in the past: Als ich ein Kind war, wohnten wir in München. = When I was a child, we lived in Munich. (single, past, completed period) wann is the question word: Wann kommst du? = When are you coming? — and also introduces indirect questions: Ich weiß nicht, wann er kommt. = I don't know when he's coming. Mixing them up is one of the clearest tells of a non-native speaker; getting them right makes everything else sound more polished.
wenn — repeated, general, conditional, future
wenn covers four overlapping situations, all of them NOT a single past event: (1) general truth / habit: Wenn es regnet, nehme ich einen Schirm. = When(ever) it rains, I take an umbrella. (2) future: Wenn ich morgen Zeit habe, rufe ich dich an. = When I have time tomorrow, I'll call you. (3) condition ('if'): Wenn du müde bist, geh schlafen. = If you're tired, go to bed. (4) repeated past: Immer wenn ich nach Berlin kam, regnete es. = Every time I came to Berlin, it rained. The clue is the word immer wenn ('every time') or some implication of repetition. As a subordinator, wenn sends the verb to the END of its clause.
als — a single, completed past event
als means 'when' ONLY for a one-time event or a single block of time, both completed and in the past. Als ich gestern nach Hause kam, war niemand da. = When I came home yesterday, no one was there. Als ich klein war, hatte ich einen Hund. = When I was little, I had a dog. Als wir in Berlin lebten, war es schön. = When we lived in Berlin, it was nice. The key test: 'did this happen ONCE in the past?' — if yes, als. als is also a subordinator, so verb at the end. (als has another job — comparing things, größer als = bigger than — but that's a separate use.)
wann — only for questions
wann is the interrogative 'when?'. Use it (1) in direct questions: Wann beginnt der Film? = When does the movie begin? Wann hast du Zeit? = When do you have time? (2) in indirect questions — i.e. embedded after a verb of asking, knowing, wondering: Ich weiß nicht, wann er kommt. = I don't know when he's coming. Kannst du mir sagen, wann der Zug ankommt? = Can you tell me when the train arrives? In an indirect question, wann is a subordinator → verb at the end of its clause. NEVER use wann for 'when I was a child' — that would be a question, which makes no sense here.
Subordinate word order — verb to the end
All three trigger the standard subordinate-clause rules from L22: the conjugated verb goes to the END of the clause. Wenn es regnet, nehme ich einen Schirm. (regnet at the end of its clause; main clause then starts with the verb because the subordinate clause sits in slot 1.) Als ich nach Hause kam, war niemand da. (kam at the end; war starts the main clause.) Ich weiß nicht, wann er kommt. (kommt at the end of the indirect question.) Separable verbs reattach: wann er ankommt, not wann er an … kommt.
Comma rules and order of clauses
Always a comma between the subordinate clause and the main clause. Either clause can come first; pick whichever puts the most important info up front. Subordinate-first → main clause inverts (verb 1st in the main): Wenn es regnet, bleibe ich zu Hause. Main-first → no inversion: Ich bleibe zu Hause, wenn es regnet. Same meaning. In speech, native speakers often prefer to lead with the subordinator for emphasis on the condition or time.
Tricky overlaps
Two situations to watch: (1) Repeated past uses wenn, not als, even though it's past. Immer wenn er kam, brachte er Blumen. = Every time he came, he brought flowers. The repetition flips it from 'one event' (als) to 'general pattern' (wenn). (2) als with damals ('back then') is very natural: Damals, als ich noch in Berlin lebte, … = Back then, when I still lived in Berlin, … (3) Indirect questions with wenn are NOT really questions — they're conditions. 'Tell me if you come' = Sag mir, ob du kommst (use ob for yes/no indirect), or Sag mir, wann du kommst (use wann for 'at what time').
Mini-checklist
Three quick questions: (1) Is it a question (real or embedded 'at what time')? → wann. (2) Is it a single, completed past event? → als. (3) Anything else (general, repeated, future, conditional)? → wenn. The vast majority of 'when' situations land on wenn; als is reserved for 'that one time in the past'; wann never describes a time, only asks about it.
