Separable verbs are verbs with one peculiarity: they separate at times. To be able to separate they must be compound verbs. Those are, e.g. ,

ein.kaufen
auf.stehen [the dots are just for illustration]
an.machen

The front part of such a verb is called Präfix. There are also prefixes that are not separable which will be covered in one of the next lessons. In a standard sentence, the prefix would detach from the core of the verb (=Stamm, m) and go to the end of the sentence:

Ich kaufe immer bei ZEWE ein.
I always shop at ZEWE.

Stehst du bitte auf!
Would you please get up?

Er macht das Licht an.
He turns the light on. <-- "to turn on" almost behaves like a German separable verb

Please note that a prefix can give a verb a completely new meaning:

machen (=to make) vs anmachen (=to turn on)
sehen (=to see) vs absehen (=to abstain)
hören (=to hear) vs aufhören (=to quit)

Behavior in dependent clauses

However, there are quite a few situations in which these verbs do not separate, e.g., in so-called subordinate or dependent clauses, which I‘ll discuss below.

Ich sehe besser, wenn ich das Licht anmache.
I see better if I turn the light on.

wenn starts a dependent clause and pushes anmachen to the end of the sentence, where it is written as one word. That is the rule for all dependent clauses, that they push their verbs to the end.

Behavior with other verbs

The same happens when separable verbs are used together with other verbs, e.g., modal verbs or in the past with haben or sein. Two examples:

Kannst du bitte das Licht anmachen?
Can you please turn the light on?

Hast du das Licht angemacht?*
Have you turned on the light?

*The -ge- is still a bit separating the verb anmachen, yet its parts are in correct order: an + mach.

How do I know which verbs are separable?

Usually you will get a quick grasp of these verbs without much struggling but there is a tiny little trick that helps identify the separable prefixes and, therefore, the separable verbs: The separable prefixes quite often correspond to prepositions. As I haven‘t covered these yet, just a quick overview of the most important separable prefixes:

Präfix resembles Präposition means in English

• aus - aus - from / out of
• bei - bei - at
• mit - mit - with
• nach - nach - towards / after
• zu - zu - to(wards)
• vor- vor - in front of / before
• an- an - on / at
• auf- auf - on top of
• ein- in - in(side)

There are other separable prefixes and prefixes that can be either separable or inseparable and there are also prepositions that resemble prefixes but are not separable. But the above nine examples will make a very solid beginning. Another way to remember which prefixes are separable is simply to learn the inseparable ones in addition to those above.