Mastronarde gives for the 2S and 3S imperfect active indicative
ἵεις and ἵει
which are thematic conjugations seemingly coming from a verb ἱέω.
I’ve looked in H&Q and I find there that in addition to the two thematic forms in the imperfect, there is also an alternate thematic form given for the 2S present active indicative
ἱεῖς
also seemingly coming from a verb ἱέω.
Mastronarde does not mention the alternate 2S present active indicative.
I was wondering if anyone could give me any historical perspective on this competition between athematic and thematic forms, and in particular is it likely or not that I will encounter the 2S present active indicative form, ἱεῖς, since Mastronarde didn’t feel it necessary to include it while H&Q did.
All -μι verbs are a mess, and ἵημι the messiest of the lot. They‘re all apt to slip into -ω-verb formations in certain parts (δεινυμι/ω most clearly but atypically). I expect Smyth gives most of the attested variants in (-)ίημι, but a better resource is LSJ, and if that doesn’t give you enough (which it should!) you could consult Veitch’s Greek Verbs Irregular and Defective, a very useful compendium (though dated). Genre makes a difference; epic forms are a law unto themselves.
How likely are you to encounter the 2sing. present active indicative form ἱεῖς, you ask? Not at all, I think, though if you read Sophocles’ Electra you might possibly encounter ἴεις (instead of ἵης). Manuscripts and editors vary, in both spelling and accentuation. Best just to read Greek texts and look up any forms you don’t recognize, given so much unpredictability as well as uncertainty.
Beware of extrapolating; e.g. 3 sing. impf ἵει is formed only as if from 1 sing. pres. ἱέω>ἰῶ, it does not imply even the potential existence of that form.
Alexandrian poets sometimes extrapolate from unusual forms, however, and expand the morphology.