brightness

noun

bright·​ness ˈbrīt-nəs 

1

a

: the quality or state of being bright

also : an instance of such a quality or state

b

: luminance

2

: the attribute of light-source colors by which emitted light is ordered continuously from light to dark in correlation with its intensity compare hue sense 2c, lightness entry 1 sense 2a, saturation sense 4

Synonyms of brightness

• brilliancy
• brilliance
• lightness
• illumination
• luminosity

Examples of brightness in a Sentence

the brightness of the sunshine made me squint after an afternoon spent in a darkened movie theater

Recent Examples on the Web

While generally a dimmer comet, recent activity has dramatically amplified 220P/McNaught’s brightness. — Andrew Paul, Popular Science, 27 Aug. 2026

The team then ran thousands of simulations, testing which combinations of globular cluster properties and dark matter distributions could reproduce the stream's observed brightness and shape. — Sharmila Kuthunur, Space.com, 26 Aug. 2026

Adaptalux says the internal battery lasts up to eight hours of continuous use depending on brightness and recharges over USB-C, which can also keep the pod running while permanently plugged in. — New Atlas, 25 Aug. 2026

This Nebula Capsule 3 projector delivers an impressive experience with 300 ANSI Lumens of brightness in 1080p, making your movies and TV shows feel lifelike. — George Yang, PC Magazine, 25 Aug. 2026

Word History

First Known Use

before the 12th century, in the meaning defined at sense 1a

Rhymes for brightness

• lightness
• rightness
• tightness
• whiteness
• finiteness
• politeness
• uprightness

Medical Definition

brightness

noun

bright·​ness ˈbrīt-nəs 

: the one of the three psychological dimensions of color perception by which visual stimuli are ordered continuously from light to dark and which is correlated with light intensity compare hue, saturation sense 4a