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
.
