1911 Encyclopædia Britannica/Optics

OPTICS, the science of light, regarded as the medium of sight (Gr. ὄψις). Generally the noun is qualified by an adjective so as to delimitate the principal groups of optical phenomena, e.g. geometrical optics, physical optics, meteorological optics, &c. Greek terminology included two adjectival forms—τὰ ὀπτικά, for all optical phenomena, including vision and the nature of light, and ἡ ὀπτική (sc. θεωρία), for the objective study of light, i.e. the nature of light itself and the theory of vision. See Light and Vision.