1
[
noncount] : the form of energy that makes it possible to see things : the brightness produced by the sun, by fire, by a lamp, etc.
The light was bright/dazzling.
The landscape was bathed/awash in light.
a ray/shaft/beam of light
a source of light = a light source
a photograph taken in low/dim light
the light of the moon
a mixture of light and shadow
The windows let fresh air and light into the room.
a plant that grows best in direct/indirect light [=with light shining directly/indirectly on it]
natural light [=sunlight]
artificial light [=light produced by electric lamps]
2
[
count]
a :
a source of light (such as an electric lamp)
turn/switch on/off the light
a fluorescent light
a light fixture [=a lamp that is permanently attached to a wall, ceiling, etc.]
a warning light
The lights suddenly went out.
The lights suddenly came on.
the twinkling lights of the city below
the bright lights of Broadway
a light switch [=a switch for turning lights on and off]
The lights are on, so there must be somebody at home.
http://learnersdictionary.com/definition/light