lux

Lux, lucis, f., third declension, stem luc-. It is light as the thing that shines, and from there the daylight and so the day itself: prima luce, "at first light", multa luce, "well into the day".

Beside it sits lumen, which is properly a light, the lamp or the source, though the two blur badly in later Latin. Metaphorically lux is safety and public view: in lucem proferre is to bring a thing to light, and a man can be the lux of his country. The family is large and useful for guessing: luceo, lucidus, Lucifer the morning star, and the name Lucius, traditionally given to a child born at daybreak.