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light 1 (līt)
1. Physics
a. Electromagnetic radiation that is visible, perceivable by the normal human eye as colors between red and violet, having frequencies between 400 terahertz and 790 terahertz and wavelengths between 750 nanometers and 380 nanometers. Also called visible light.
b. Electromagnetic radiation of any frequency or wavelength.
2. The sensation of perceiving light; brightness: a sudden light that made me blink.
a. A source of light, especially a lamp, a lantern, or an electric lighting fixture: Turn out the lights when you leave.
b. The illumination derived from a source of light: by the light of the moon.
c. The particular quantity or quality of such illumination: moved the lamp closer to get better light.
d. The pathway or route of such illumination to a person: You're standing in his light.
a. A source of fire, such as a match or cigarette lighter.
b. A mechanical device that uses illumination as a signal or warning, especially a beacon or traffic signal.
a. Daylight.
b. Dawn; daybreak.
6. Something, such as a window, that admits illumination.
7. Architecture One of two or more openings in a window divided by a mullion or mullions.
8. Something that provides information or clarification: research that produced little new light on the question.
a. A state of awareness or understanding, especially as derived from a particular source: in the light of experience.
b. Public attention; general knowledge: brought the scandal to light.
c. Spiritual awareness; illumination.
10. A way of looking at or considering a matter; an aspect: saw the situation in a different light.
11. Archaic Eyesight.
12. lights One's individual opinions, choices, or standards: acted according to their own lights.
13. A person who inspires or is adored by another: My daughter is the light of my life.
14. A prominent or distinguished person; a luminary: one of the leading lights of the theater.
15. An expression of the eyes: a strange light in her eyes.
16. lights Pieces of laundry that are not dark in color.
17. Light In Quaker doctrine, the guiding spirit or divine presence in each person.
v. light·ed or lit (lĭt), light·ing, lights
1. To set on fire; ignite or kindle: lit the kindling.
2. To cause to give out light; make luminous: lit a lamp.
3. To provide, cover, or fill with light; illuminate: fireworks lighting the sky.
4. To signal, direct, or guide with light: "You'd ... set the lamp in the dormer window to light him home through the storm" (Edith Nesbit).
5. To enliven or animate: A smile lit her face.
1. To start to burn; be ignited or kindled: Green wood does not light easily.
2. To emit light; be lighted: Wait until the indicator lights up.
adj. light·er, light·est
a. Having a greater rather than lesser degree of lightness.
b. Of or being an additive primary color.
2. Characterized by or filled with light; bright: a room that is light when the shutters are open.
3. Not dark in color; fair: light hair and skin.
4. Served with milk or cream. Used of coffee.
Phrasal Verb:
light up
1. To become or cause to become animated or cheerful.
2. To start smoking a cigarette, cigar, or pipe.
cast/shed/throw light on
To provide information about or clarify (something).
in (the) light of
In consideration of; in relationship to.
light a fire under
To urge or move to action.
light at the end of the tunnel
The prospect of success, relief, or escape after strenuous effort.

[Middle English, from Old English lēoht, līht; see leuk- in the Appendix of Indo-European roots.]

Usage Note: Lighted and lit are equally acceptable as past tense and past participle of light. Both forms are also well established as adjectives: a lighted (or lit) candle.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.