Separable verbs (or in German "trennbare Verben") are confusing for many students. First, many struggle to identify them. Second, they don't understand when they split and when they don't. So in this post I'm going to explain separable verbs in the German language.
How do you identify separable verbs? This category of verbs is comprised of two parts: a prefix and a core verb. The prefix is always one syllable and normally a preposition like "an", "auf", "aus". The second part, which I call "core verb", is usually a verb that exists as an independent verb. Let's look at common examples:
aufstehen (to get up)
ankommen (to arrive)
ausgehen (to go out)
Stehen (to stand), kommen (to come), and gehen (to go) are verbs in their own right. So, as a rule of thumb, when a verb that exists on its own is part of a longer verb with a prefix at the start, assume it's a separable verb. Other examples of separable verbs are
einkaufen (to shop)
fernsehen (to watch television)
anfangen (to start)
einschalten/ausschalten (to switch on/off)
anstoßen (to toast)
Now that you should find it easier to identify separable verbs, let's discuss when they split and when they don't. This is actually more straight forward than you might think. The rule is whenever the separable verb is the only verb in a main clause, it splits and the prefix moves all the way to the end of your sentence, while the core verb gets conjugated in second place. That means that whenever there are two verbs in a main clause (an auxiliary verb and a separable) or in a subordinate clause, separable verbs do not split. Let's look at examples again:
Ich stehe morgens normalerweise um 7 Uhr auf.
Sie kommen gegen 12 Uhr in Hamburg an.
Wir gehen am Wochenende aus.
In these three main clauses, the separable verb is the only verb, hence it splits. Let's add some auxiliary verbs to these sentences to see that the separable verbs do not separate then.
Ich muss morgens normalerweise um 7 Uhr aufstehen.
Sie werden gegen 12 Uhr in Hamburg ankommen.
Wir wollen am Wochenende ausgehen.
As you will see in the below examples, separable verbs don't split in subordinate clauses:
Da ich morgens normalerweise um 7 Uhr aufstehe, versuche ich vor Mitternacht ins Bett zu gehen.
Wenn sie gegen 12 Uhr in Hamburg ankommen, haben sie genug Zeit, die Stadt zu sehen.
Obwohl wir am Wochenende ausgehen, arbeiten wir auch jeden Sonntag.
So, as the examples have shown, separable verbs only ever split in a main clause and when they are the only verb.
There are some prefixes, though, that introduce non-separable verbs, so need to be treated as exceptions to the above rules:
e.g. bezahlen, entscheiden, erwarten, verdienen, zerstören.
Er bezahlt die Rechnung.
Sie entscheidet sich für ein Studium.
Wir erwarten ein Ende der Pandemie.
Sie verdient ziemlich gut.
Der Tornado zerstört viele Häuser.
Finally, there are some prefixes that do not tell you whether the verb is separable or not. So you need to learn it with the verb:
e.g. wiederkommen (separable verb) vs. wiederholen (non-separable verb)
Wir kommen gleich wieder vs. Wir wiederholen trennbare Verben.
However, my advice would be not to concentrate on the exceptions too much as they make separable verbs seem like a messier grammatical topic than it actually is. Instead, concentrate on the rule that separable verbs split whenever they are the only verb in a main clause and pick up the exceptions as you progress in your German course.
Learn about other grammar topics on our German language blog "Auf Deutsch, bitte!". There you'll find posts explaining the four cases, on the Perfekt tense, German pronouns in general and the difference between mir and mich, sein and ihr more specifically, how to use the pronoun man, adjective ending rules, two-way prepositions, German word order and many more.
Many German students wonder which online dictionary they should use. Read my answer and let me know what you think in the comments.