- εἰδέα (later Greek)
- ἰδέη (Ionic)
From ἰδεῖν, the infinite of εἶδον, the aorist of the hypothetical verb εἴδω, which only appears in past tense.
- (5th BC Attic): IPA: /idé.a͜a/
- (1st BC Egyptian): IPA: /idɛ́aː/
- (4th AD Koine): IPA: /iðéa/
- (10th AD Byzantine): IPA: /iðéa/
- (15th AD Constantinopolitan): IPA: /iðéa/