English

light equation

From light (noun) + equation (noun).

Proto-Indo-European *lewk- ‘to shine’

…

Proto-Germanic *leuhtą

Proto-West Germanic *leuht ‘light’

Old English lēoht

Middle English light ‘light, illumination’

English light

Old Latin aiquos

Latin aequus ‘equal’

Latin aequō ‘make equal or level’

Latin aequātiō ‘an equalizing’

Today it means

noun The time which light takes to traverse the mean distance of the Earth from the Sun.

Language periods are conventional ranges, not dates for this word.

Etymograph / light equation