<p><strong>noun</strong></p><ul><li>Luminance (def 2).</li><li>The quality of being intellectually brilliant, enlightened, inspired, etc.: The luminosity of his poetry is unequaled.</li><li>Something luminous.</li><li>Astronomy: 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.</li><li>Also called luminosity factor.</li><li>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.</li></ul>