25.15 The remaining –μι verbs on our list all begin with a vowel or diphthong. If the verb stem begins with a SHORT vowel or DIPHTHONG, the augment ἐ– is not added (though see ἔχω, ἕξω/σκήσω below, for an exception). Rather, the initial short vowel itself, including the short vowel of a diphthong, is augmented through LENGTHENING (S 435, G 265b)!
25.16 Short initial vowels lengthen as follows when augmented:
If the initial vowel is long – e.g. ἡδύνω sweeten – no lengthening occurs, since the vowel is already long.
(cf. S 416)
This verb has an initial vowel augment, but it does not affect the way the vowel is written, since long and short ι are written the same.
As with ἵστημι, this verb has a long vowel augment, but it does not affect the way ι is written. Notice also that, as with τίθημι, this verb uses –ει– here in the 2nd and 3rd person singular (S 746b).
The irregularities of the imperfect of εἰμί are many, and require memorization (S 771, G 384).
