The classical prefixes for inseparables are:

be  – ent – er – ge – ver – zer

bekommen          –        get

entdecken            –        discover

erfahren               –        experience

gehören                –        belong

vergessen             –        foget

zerstören              –        destroy

Theses prefixes are always unstressed. That makes that a compound verb preceded by one of  these prefixes will always be inseparable.

There is no  „ge“-marker in the past participle of inseparable verbs! – e.g.: verloren, and not geverloren or vergeloren!

Some unseparables on the basis of regular verbs:

besuchen      –        visit

zerstören      –        destroy


list of separable and non-separable verbs:

separable and inseparable verbs