Present Indicative      Contract verbs   Contractions I fill       πληρό-ω => πληρῶ    ό  + ω  => ῶ you (sg.) fill   he/she/it fills       πληρό-εις     πληρό-ει =>  =>  πληροῖς πληροῖ    ό  + ει  => οῖ we fill       πληρό-ομεν => πληροῦμεν  ό  +  ο  => οῦ you (pl.) fill       πληρό-ετε => πληροῦτε    ό  +  ε  => οῦ they fill       πληρό-ουσιν => πληροῦσιν    ό  + ου => οῦ       Imperative   Contract verbs   Contractions eh you, fill!      πλήρο-ε => πλήρου    ο  +  ε  => ου (you all) fill!        πληρό-ετε => πληροῦτε    ό  +  ε  => οῦ       Infinitive   Contract verbs   Contractions to fill       πληρό-ειν => πληροῦν    ό  +  ει  => οῦ *    * Note  This looks like a mistake, but it isn't. It is because the infinitive ending ειν is actually a contraction itself of ε + ε becoming ει. So we get a double contraction, first stem πληρό + ε + εν becomes πληρού + εν becomes πληροῦν. The same does happen with -ε contractions, though it looks like there was just one normal contraction of έ + ειν becoming εῖν. For the simple reason that: πονέ + ε + εν becomes πονεί + εν becomes πονεῖν