μέγεθος , Ion. (not Hp.) μέγα^θος Hdt. (v. infr.), also Philox.2.19, εος, τό
So says LSJ. It shows up in Pl. Ap., but I don’t know how to decline it as all I know is Attic. How do you decline it, or where can I find out how to decline it quickly (online)? Is there a grand table of all Greek declensions somewhere?
Thanks in advance.
Can you please post the reference in Plato’s Apology?
I’ve searched and could not find it in any case.
Sure, 30e:
ἐὰν γάρ με ἀποκτείνητε, οὐ ῥᾳδίως ἄλλον τοιοῦτον εὑρήσετε, ἀτεχνῶς—εἰ καὶ γελοιότερον εἰπεῖν—προσκείμενον τῇ πόλει ὑπὸ τοῦ θεοῦ ὥσπερ ἵππῳ μεγάλῳ μὲν καὶ γενναίῳ, ὑπὸ μεγέθους δὲ νωθεστέρῳ καὶ δεομένῳ ἐγείρεσθαι ὑπὸ μύωπός τινος…
Thanks for the reference, pster. 
I think the way LSJ lists the entries is first giving the common form, which in most cases is Attic,
then the Ionic and other dialects if there is any difference. Here we have the Attic form,
μέγεθος, and then the Ionic one [Herodotus, though not Hp.(? can’t find this abbreviation
anywhere)], μέγᾰθος.
I find only μεγέθεος as the Ionic gen. sg., not μεγάθεος,
whereas Plato had used the contracted Attic μεγέθους.
Hp. = Hippocrates