When forming the past participle of verbs ending in -ieren you will often leave out the ge- prefix. Otherwise, they work just like other weak verbs.
Infinitive | Stem | Past Participle |
---|---|---|
servieren to serve | servier- | serviert served |
studieren to study | studier- | studiert studied |
kopieren to copy | kopier- | kopiert copied |
Many German verbs ending in -ieren are loanwords from other languages such as French.