infrared

adjective

in·​fra·​red ˌin-frə-ˈred 

-(ˌ)frä-,

-fə-

1

: situated outside the visible spectrum at its red end

—used of radiation having a wavelength between about 700 nanometers and 1 millimeter

2

: relating to, producing, or employing infrared radiation

infrared therapy

3

: sensitive to infrared radiation

infrared sensors that detect body heat

infrared noun

Examples of infrared in a Sentence

Recent Examples on the Web

Astronomers have uncovered a remarkable new addition to the catalog of ultra-luminous infrared galaxies (ULIRGs) – cosmic powerhouses that shine with more than a trillion times the luminosity of our Sun and forge stars at astonishing rates of up to a thousand solar masses per year. —Bojan Stojkovski, Interesting Engineering, 12 Oct. 2025

This smart cat litter box uses infrared sensors to detect when your cat is finished, then automatically scoops and cleans itself, dramatically reducing odors with an ionic deodorizer. —Christine Persaud, USA Today, 11 Oct. 2025

The overall rate, (left) is derived from both ultraviolet and infrared observations, and is remarkably consistent across time and space. —Big Think, 10 Oct. 2025

More than 25 years ago, dermatologist Albert Kligman reported that infrared radiation could worsen the effects of UV light and, on its own, trigger skin damage similar to that of UV light. —Leslie Baumann, Miami Herald, 9 Oct. 2025

Word History

First Known Use

1881, in the meaning defined at sense 1

Phrases Containing infrared

• far-infrared
• near-infrared

Rhymes for infrared

• abovesaid
• aforesaid
• arrowhead
• casinghead
• copperhead
• figurehead
• fountainhead
• gingerbread
• hammerhead
• leatherhead
• letterhead
• loggerhead

Kids Definition

infrared

adjective

in·​fra·​red ˌin-frə-ˈred 

-(ˌ)frä-

: being, relating to, producing, or using rays like light but lying outside the visible spectrum at its red end

infrared radiation

infrared noun

Medical Definition

infrared

1 of 2 adjective

in·​fra·​red ˌin-frə-ˈred 

1

: lying outside the visible spectrum at its red end

—used of radiation having a wavelength between about 700 nanometers and 1 millimeter

2

: relating to, producing, or employing infrared radiation

infrared therapy

infrared

2 of 2 noun

: infrared radiation