What is the difference between "als" and "wenn" in German?
There are a few subordinate clause conjunctions that students find difficult to use. The conjunctions "als' and "wenn" are often considered to be particularly confusing. While both might often be translated as 'when' in English, they’re used in a completely different way.
"Als" is used for completed actions and hence in the past, whereas "wenn" is used for recurring events, irrespective of the tense. Let's take a look at some examples:
Als ich ein Kind war, wohnte ich in Deutschland.
Ich verließ das Haus, als es anfing zu regnen.
So "als" is the English "when" but only in the past.
Wenn ich morgens aufstehe, gehe ich zuerst ins Badezimmer.
Wenn du dein Deutsch verbessern möchtest, musst du regelmäßig üben.
"Wenn" is best translated as "whenever", as in the first example, or "if" as in the second.
Often, teachers say that "wenn" cannot be used in the past. This is incorrect. The main usage of "wenn" in the past is in the German subjunctive (Konjunktiv 2).
e.g. Wenn ich früher mehr Vokabeln gelernt gelernt hätte, wäre mein Griechisch heute besser.
For English native speakers who try to translate the English "when", there is another word that confuses matters further and that is the question word "wann". However, "wann" can in fact only be used in questions and is therefore quite different from the subordinate clause conjunctions "als" and "wenn".
e.g. Wann beginnt dein Deutschunterricht?
Alas, "wann" can also be used in indirect questions which do subordinate.
e.g. Ich frage mich, wann dein Deutschunterricht beginnt.
It is still a question word, though, whereas "als" and "wenn" are not.
One final note on "als" in German. It is a confusing word because it comes up in different grammatical contexts. Check out my blog post on the topic to avoid confusion.
Learn more about German word order in main and subordinate clauses on my blog. There, you will also find posts about the difference between nachdem and danach, bevor and vorher, when to use zu in German sentence, an explanation of how to use um...zu and damit, and a post about words such as als, ohne, statt, seit, and um that be used in different grammar contexts.
Related topics we discuss on our blog are relative clauses in German, the German cases, and adjectival endings in German, and the Konjunktiv 2 subjunctive in German. There, you will also find reviews about online German dictionaries and apps for learning German.