Proto-Indo-European root meaning "light, brightness."
It forms all or part of: allumette; elucidate; illumination; illustration; lea; leukemia; leuko-; light (n.) "brightness, radiant energy;" lightning; limn; link (n.2) "torch of pitch, tow, etc.;" lucent; lucid; Lucifer; luciferase; luciferous; lucifugous; lucubrate; lucubration; luculent; lumen; Luminal; luminary; luminate; luminescence; luminous; luna; lunacy; lunar; Lunarian; lunate; lunation; lunatic; lune; lunette; luni-; luster; lustrum; lux; pellucid; sublunary; translucent.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit rocate "shines;" Armenian lois "light," lusin "moon;" Greek leukos "bright, shining, white;" Latin lucere "to shine," lux "light," lucidus "clear;" Old Church Slavonic luci "light;" Lithuanian laukas "pale;" Welsh llug "gleam, glimmer;" Old Irish loche "lightning," luchair "brightness;" Hittite lukezi "is bright;" Old English leht, leoht "light, daylight; spiritual illumination," German Licht, Gothic liuhaþ "light."
"broad, dark area of the moon," 1765, from Latin mare "sea" (from PIE root *mori- "body of water"). Applied to lunar features by Galileo and used thus in 17c. works written in Modern Latin. They originally were thought to be actual seas.
"a crescent or crescent-shaped body," 1690s in reference to lenses convex on one side, concave on the other, and thicker in the middle; c. 1812 in reference to liquid surfaces, Modern Latin meniscus, from Greek meniskos "lunar crescent," diminutive of mene "moon" (see moon (n.)). Related: Meniscoid; mensicoidal; mensical; mensicate.
1650s, "act of carrying out or away," from Late Latin evectionem (nominative evectio) "a carrying upward, a flight," from Latin evehere, from assimilated form of ex "out of, from within" (see ex-) + vehere "to carry" (from PIE root *wegh- "to go, move, transport in a vehicle"). Astronomy sense, "second lunar inequality," is from 1706.