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

And everything has a different relationship with infrared light. — Georg Szalai, HollywoodReporter, 9 Sep. 2026

Davyne’s near-infrared response can be switched on and off, allowing security markings to appear for inspection and then become invisible again. — Sujita Sinha, Interesting Engineering, 7 Sep. 2026

Its 1,400-watt infrared heater quietly emits nearly 5,000 Btu of heat, but the exterior remains cool to the touch. — Bestreviews, Chicago Tribune, 7 Sep. 2026

Using huge infrared telescopes that can see through that veil of dust, astronomers have been able to watch some of these stars swirling around the black hole. — Phil Plait, Scientific American, 4 Sep. 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