διεφθάρμην

This is a pluperfect, at least according to Mastronarde’s verb drills, but why isn’t there an eta augment? Why is the epsilon retained?

Thanks in advance.

The verb stem is φθείρω. When a verb starts with a consonant cluster other than stop + liquid, there is no reduplication but an augment ἐ-. That augment doesn’t get further augmentation in the pluperfect. Smyth §444, “when the perfect stem begins with a vowel the pluperfect retains the prefix of the perfect.”

Thanks. I seemed to have encountered mostly Attic reduplications lately which do lengthen the vowel (Smyth 446), so I thought they were all like that.