light (illumination)
light (source of illumination)
light, daylight (level of illumination appropriate for a particular time of day or year)
(colloquial) power, current (electric flow)
clearance, interstitial space (area between walls)
lumen (cavity or channel within a tube or tubular organ)
spacing (space between lines or words in the text)
light (place in a photograph or painting that is distinguished by a lighter color)
(informal) traffic lights (street intersection with traffic lights)
(obsolete) gap (space between ties or rails)

clear, understandably