- luxIn the International System of Units, the derived unit of illuminance or illumination; one lumen per square metre. Symbol: lx
- luxonAny particle that travels at exactly the speed of light and has zero mass: typically a photon.
- luciformHaving, in some respects, the nature of light; resembling light.
- lucigenA kind of oil lamp using compressed air.
- lucigeninAn aromatic compound, bis-N-methylacridinium nitrate, that exhibits a bluish-green fluorescence.
- lucigraphAn apparatus for displaying letters and numbers in international maritime code used for signalling.
- lucimeterAn instrument used to measure light intensity.
- luculefacula (bright spot on the sun)