ἰδέα
Etym. ἰδεῖν
I. = εἶδος, "form", Pind., Ar., etc.
2. "the look" of a thing, as opp. to its reality, Lat. species, γνώμην ἐξαπατῶσ᾽ ἰδέαι "outward appearances" cheat the mind, Theogn.
3. "a kind, sort, nature", Hdt.; ἐφρόνεον διφασίας ἰδέας they conceived two "modes" of acting, id=Hdt.; τὰ ὄργι᾽ ἐστὶ τίν᾽ ἰδέαν ἔχοντα; what is their "nature or fashion?" Eur.; καινὰς ἰδέας εἰσφέρειν to bring in new "fashions", Ar.; πᾶσα ἰδέα θανάτου every "form" of death, Thuc.
II. in Logic, = εἶδος, "a class, kind, sort, species", Plat.