Untranslatably, both headword and gloss are single nouns in the Greek.
Same entry, i.e. with nominative plurals, in the Synagoge and Photius, but earlier Hesychius kappa343 had a very similar one with either accusative plurals or genitive singulars (i.e. the ambiguous --ias suffix); and cf. also the scholia to Homer, Iliad 15.16, where the genitive singular appears (-i/hs there: web address 1 below).