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

Most show footage from an infrared camera tracking a white object that appears as a speck on the screen moving through the air. —Stefan Becket, CBS News, 8 May 2026

Now, using a system designed and built by the Fraunhofer Center for Applied Photonics in Glasgow, Vector Photonics’ PCSELs transmitted data through open air at the near-infrared wavelength of 1310 nanometers—in telecom’s O-band, a familiar wavelength for fiber-optic communications. —IEEE Spectrum, 7 May 2026

Lidar systems help autonomous vehicles detect obstacles and map surroundings using pulses of infrared light. —Aamir Khollam, Interesting Engineering, 7 May 2026

Current ways of measuring mass loss from, say, infrared or radio observations, typically only show us what's happening right now. —Paul Sutter, Space.com, 3 May 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