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

The team investigated the mechanism using in-situ Fourier-transform infrared spectroscopy and density functional theory calculations. — Alexandra Harrell, Footwear News, 26 Aug. 2026

The staff is also quick to offer assistance in securing a reservation for dinner at Matilda or booking the wellness room, which has an infrared sauna facing the mountains and a small area with workout equipment. — Condé Nast, Condé Nast Traveler, 26 Aug. 2026

Firefighters, for instance, use infrared trackers on burning buildings from the outside to see where the source of the fire might lie within. — Monisha Ravisetti, Space.com, 25 Aug. 2026

The resulting material reflects nearly 88% of incident sunlight while emitting just over 96% of its light in the mid-infrared range. — Mike McRae 24, New Atlas, 24 Aug. 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