Eikonal 近似
忘れないうちに調べておく.
īcōn, onis, f. 像,形.
εἰκών, ἡ, gen. όνος, acc. όνα, etc.: poët. and Ion. forms (as if from εἰκώ) gen. εἰκοῦϛ, acc. εἰκώ, pl. εἰκοῦϛ: (*εἴκώ, ἔοικα): ―a likeness, image, portrait, Hdt., Aesch.
2. an image in a mirror, Eur., Plat.
II. a semblance, phantom, Eur., Plat., etc.: an image in the mind, Id.
III. a similitude, similé, Ar., Plat.