οὐσία
Alt. οὐσία, ἡ,
Etym. οὖσα, part. fem. of εἰμι
I. "that which is one's own, one's substance, property", Hdt., Eur.
II. = τὸ εἶναι, "being, existence", Plat.; τὰς ἄπαιδας οὐσίας her childless "state", Soph.
III. "the being, essence, nature" of a thing, Plat., etc.