/looh'meuh nos"i tee/ , n. , pl. luminosities .
1. luminance (def. 2).
2. the quality of being intellectually brilliant, enlightened, inspired, etc.: The luminosity of his poetry is unequaled.
3. something luminous.
4. Astron. the brightness of a star in comparison with that of the sun: the luminosity of Sirius expressed as 23 indicates an intrinsic brightness 23 times as great as that of the sun.
5. Also called luminosity factor . Optics. the brightness of a light source of a certain wavelength as it appears to the eye, measured as the ratio of luminous flux to radiant flux at that wavelength.
[ 1625-35; luminos ( us ) LUMINOUS + -ITY ]