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

New infrared observations reveal the rare interstellar visitor comet 3I/ATLAS dramatically brightening during its farewell tour of the solar system. —Samantha Mathewson, Space.com, 6 Feb. 2026

Most of the galaxies in the Universe are small and faint; most of the stars in the Universe emit primarily red or even infrared light; most of the galaxies in the Universe are rich in dust; most of the Universe that’s observable to us are located at significant cosmic distances. —Big Think, 4 Feb. 2026

Short-wave infrared imaging (SWIR), is one of the most recent developments in this technology, allowing users to see through materials like vehicle windshields and expanding its use in transportation, inspection, and safety applications. —Atharva Gosavi, Interesting Engineering, 4 Feb. 2026

Currently on Kickstarter, the HeatWave Go is a self-heating lunch box that uses infrared technology to warm up meals. —New Atlas, 4 Feb. 2026

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