A signalling device positioned at a road intersection or pedestrian crossing to indicate when it may be safe to drive, ride or walk, using a universal colour code.

A switch, usually mounted on a wall in a building, used to turn the light on or off.

(astronomy) A soft glow of white light seen in the sky along the ecliptic in an elongated triangular form with its base being on the horizon, particularly in the tropics.

One of a race of elves who live above ground and are radiant. / (Norse mythology) A daylight dwelling elf or nature spirit (as opposed to the underground dwelling dark elves or dwarves).

(physics) The speed of electromagnetic radiation; in a perfect vacuum it is defined as 299,792,458 metres per second / (colloquial, figuratively) A very rapid speed.

(intransitive, cricket, of the umpires) To ask the batsmen if they wish to continue playing in conditions of poor light. If they do not, play is suspended for bad light.

(cricket) A weather condition where the light is so poor that the umpires feel that to continue playing would be dangerous. / (figuratively) An unfavourable presentation.

A source of illumination.

(cricket) The lighter of the rollers used for flattening the pitch between innings.

synchrotron radiation