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

By measuring the tiny drop in the system's total brightness during each eclipse, the team could isolate the planet's infrared glow and directly determine its dayside temperature. —Sharmila Kuthunur, Space.com, 11 Dec. 2025

But the second event observed, dubbed Nova Cassiopeiae 2021, discovered in March 2021, became brighter within two days of discovery; the brightness halted for a couple of weeks; then reached a brightness peak about 53 days after initial discovery. —Keith Matheny, Freep.com, 11 Dec. 2025

Unboxing it, knowing those fragrant white blooms would soon fill my home with brightness and beauty for weeks, brought pure joy. —Sarah Lyon, Southern Living, 11 Dec. 2025

The 150-mAh battery, which charges over USB-C, will power the primary light at full 300 lumen brightness for 45 minutes, and stretch to 26 hours with the intensity turned all the way down. —Abhimanyu Ghoshal, New Atlas, 10 Dec. 2025

Word History

First Known Use

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

Rhymes for brightness

• lightness
• rightness
• tightness
• whiteness
• 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