Perfect

 

In inseparable verbs, the past participle (Partizip II) is formed without the use of  the "ge" prefix. See more at Past Participle with/without -ge-.

 

Examples        
begehen
be
+
gang-en
begangen
verstehen
ver
stand-en
verstanden
         
infinitive
verb prefix
+
present perfect stem & ending -en
past participle (Partizip II)