a. [ Cf. F. réfractif. See Refract. ] Serving or having power to refract, or turn from a direct course; pertaining to refraction;
Refractive index. (Opt.)
Absolute refractive index (Opt.),
Relative refractive index (of two media) (Opt.),
n. The quality or condition of being refractive. [ 1913 Webster ]