Vowel changes when forming the past participle Here are examples of the most common vowel changes when forming the past participle (for the perfect tense). For example, the past participle of beginnen is begonnen - the i changed into an o. Can you match them all up? Activity created by R. Lloyd. Tools See a list of terms used in this activity. This activity was created by a Quia Web subscriber. To learn how to make your own, just like this, click here.