Χαίρετε!
I have been struggling with how to get the imperfect of ἐμπίμπλημι. Is it normal for an ἐμ to switch to an ἐνε when switching from primary to secondary tenses?
Χαῖρε!
ἐμπίμπλημι is a composite verb formed as a combination of the preposition ἐν + the simple verb πίμπλημι. In such combinations, the ν of the preposition changes according to the initial consonant of the verb. In this case, we have the labial π which prompts to change the ν into a μ (which as another labial facilitates the pronunciation). In secondary tenses, the augment is inserted between the prepostion and the simple verb, and the preposition turns back to its original form ἐν-ε-πίμπλη (in this case 3rd p. sg. ind. imperf. act.)
Εὐχαριστῶ!