light meter noun (photography)

A meter for measuring the level of light present, an exposure meter

lightˈ-mill noun

A radiometer

lightˈ-orˈgan noun

A keyboard instrument that gives a play of light as an organ gives sound

light pen noun (computing)

1. A pen-shaped photoelectric device that can communicate directly with a computer, entering or altering data on a screen
2. A light-sensitive fibre-optic device shaped like a pen, used for reading barcoded labels

light pollution noun

The unpleasant effects of excessive artificial lighting, esp in large cities

lightˈ-proof adjective

Impervious to light, light-tight

lightˈship noun

A ship serving the purpose of a lighthouse

light show noun

A colourful spectacle of moving lights that often accompanies rock and pop bands at live performances, usu projected onto a large screen

light table noun (printing)

(a table incorporating) a ground-glass surface, illuminated from below, for use when working on lay-out with translucent materials

light therapy noun

The use of artificial light to treat depression, fatigue and disorders such as SAD, thought to be caused by insufficient natural light for the body's needs

lightˈ-tight adjective

Light-proof

light time noun

The time taken by light to travel from a heavenly body to the observer

lightˈ-tower noun

light trap noun

Any mechanical arrangement which permits movement while excluding light, such as the doors and partitions providing access to a darkroom

lightˈ-year noun

The distance light travels in a year (about 6000000000000 miles)

according to one's lights

As far as one's knowledge, spiritual illumination, etc enables one to judge

between the lights

In the twilight

between two lights

Under cover of darkness

bring to light

To reveal

come to light

To be revealed

fixed light

In lighthouses, an unchanging light

floating light

A light at the masthead of a lightship

go out like a light

To fall sound asleep soon after going to bed

hide one's light under a bushel see under bushel¹

in a good (or bad) light

Putting a favourable (or unfavourable) construction on something

inner light

Spiritual illumination, esp divinely inspired

in one's (or the) light

1. Positioned between the speaker or the stated person and the source of illumination
2. Blocking one's chance of success

in the light of

Considering, taking into account

leading light see under lead¹

light at the end of the tunnel

An indication that success, completion, etc is assured, if still distant

light of nature

1. Intellectual perception or intuition
2. Man's capacity of discovering truth unaided by revelation (theology)

lights out

1. A bugle or trumpet call for the extinction of lights (military)
2. The time at which lights are turned out for the night, in a boarding school, barracks, etc

light up

1. To light one's lamp, pipe, cigarette, etc
2. To turn on the light
3. To make or become light, bright, happy, etc

lit (up)

Drunk

northern and southern lights

Aurora borealis and australis respectively

see the light

1. To come into view or being
2. To realize a fact, mistake, etc
3. To be religiously converted

see the light of day

1. To be born, discovered or produced
2. To come to public notice

shed, throw or cast light on

To clarify, help to explain

stand in one's own light

To hinder one's own advantage

strike a light! (slang)

An exclamation expressing surprise