etendue

== English == === Etymology === Borrowed from French étendue (“area, expanse; size; extent, range, scale”), short for étendue géométrique (“geometric extent”). === Pronunciation === (Received Pronunciation) IPA(key): /ˌeɪ.tɒnˈd(j)uː/ (General American) IPA(key): /ˌeɪ.tɑnˈdu/ Rhymes: -uː Hyphenation: eten‧due === Noun === etendue (uncountable) (optics) A conserved property of the light in an optical system which characterizes how "spread out" the light is in terms of angle and area: it is the product of its cross-sectional area (normal to the direction of propagation) and the solid angle it subtends. Synonyms: AΩ product, acceptance, geometric extent, light-collecting power, light-gathering power, light grasp, optical extent, throughput ==== Alternative forms ==== étendue ==== Translations ====