An Etymological Dictionary of Astronomy and Astrophysics

The luminous intensity in a given direction of a small element of surface area divided by the orthogonal projection of this area onto a plane at right angle to the direction. It is measured in candelas per square meter. Luminance is often called surface brightness of the object.

Etymology (EN): From lumin-, combining form of → lumen “light,” + -ance a suffix used to form nouns either from adjectives in -ant or from verbs.

Etymology (PE): Tâbâni, from tâbidan “to shine,” → luminous.