I am just a beginning student of German and recently read about separable and inseparable verb prefixes. It made me curious about the frequency of each in the German language. Does anyone know the answer to this?
9176 Einträge der Flexionsklasse Trennbare Verben von insgesamt 18202 Verben im Canoo Wörterbuch.
Hence, in this (incomplete) database there are roughly 50% of verbs listed as separable.
I assume frequency refers to how often separable prefixes are used on a regular day, so the answer is: a whole lot. You will definitely need to understand the various meanings of separable and inseparable verb prefixes in order to have command of the language.
It's hard to say exactly the most used separable and inseparable prefixes, but I found a few interesting pages that can help you understand the meaning of the most commonly used verb prefixes.
Bonus Mini Lesson
The concept of prefix separation is not too complicated once you differentiate the separable and inseparable prefixes. For example,
Verb: abschließen (to lock)
Separable Prefix: ab-
Verb Root: schließen (to close, to shut)
Er schließt die Tür ab. (He is locking the door.)
Er muss die Tür abschließen. (He has to lock the door.)
Er hat die Tür abgeschlossen. (He closed the door.)
In the second sentence, the verb and prefix are not separated because there is another verb which precedes it (müssen). In the third sentence, however, a -ge- is added in between the separable prefix and the verb root. This is common with many separable verbs when used in the past tense.
Verb: besuchen (to visit)
Inseparable Prefix: be-
Verb Root: suchen (to search, to seek)
Er besucht seine Mutter. (He is visiting his mother.)
Er muss seine Mutter besuchen. (He has to visit his mother.)
Er hat seine Mutter besucht. (He visited his mother.)
In all cases and tenses, the inseparable prefix is attached to the verb root.