POSSUM - past perfect (Latin pluperfect) tense - (copy) The verb possum posse potui -- be able, can, is formed by using sum with the prefix pos- or pot-. Notice that pos- precedes a consonant, while pot- precedes a vowel. Unscramble the Latin word that fits the definition. Tools This activity was created by a Quia Web subscriber. To learn how to make your own, just like this, click here.