infrared

or in·fra-red

[ in-fruh-red ]

See synonyms for infrared on Thesaurus.com

noun

the part of the invisible spectrum that is contiguous to the red end of the visible spectrum and that comprises electromagnetic radiation of wavelengths from 800 nanometers to 1 millimeter.

adjective

noting or pertaining to the infrared or its component rays: infrared radiation.

Compare Meanings

infrared vs. ultraviolet

Click for a side-by-side comparison of meanings. Use the word comparison feature to learn the differences between similar and commonly confused words.

Origin of infrared

First recorded in 1825–35; infra- + red¹

Compare ultraviolet.

Words Nearby infrared

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use infrared in a sentence

This technology, called functional near-infrared spectroscopy, is the same that allows pulse oximeters to measure oxygen levels in the blood.
Can privacy coexist with technology that reads and changes brain activity? | Laura Sanders | February 11, 2021 | Science News
The operator gets a real-time view of what Spot sees and hears through its onboard sensors, which include an infrared camera.
Boston Dynamics gave its dog-like robot a charging dock and an arm on its head | Stan Horaczek | February 2, 2021 | Popular-Science
Wi-Charge’s PowerPuck system employs infrared beams that can power low-draw devices from up to 30 feet away without the power level dropping as you move further away.
Xiaomi’s long-range wireless charger shows a glimpse of a cord-free future | Stan Horaczek | February 1, 2021 | Popular-Science
We suggest reaching for a ceramic, porcelain, or infrared dryer, which will gently dry your hair without sucking up healthy moisture.
The best hair dryer: Get a salon-worthy blowout at home | Carsen Joenk | January 22, 2021 | Popular-Science
He and his team are now looking at another type of light called the cosmic infrared background.
Our feverish universe is getting hotter every day | Christopher Crockett | January 11, 2021 | Science News For Students

Therefore, it is not possible for any F-35 schedule to include a video data link or infrared pointer at this point.
Pentagon Misfires in Stealth Jet Scandal | Dave Majumdar | January 8, 2015 | THE DAILY BEAST
Some pilots consider the infrared marker to be crucial to the close air-support mission to support ground troops.
Newest U.S. Stealth Fighter ‘10 Years Behind’ Older Jets | Dave Majumdar | December 26, 2014 | THE DAILY BEAST
infrared light does not have a color which means it cannot be seen by the human eye.
Richard Mosse Photographs War in Technicolor | Nico Hines | April 11, 2014 | THE DAILY BEAST
Unlike humans, it can watch for days, even years, watch an entire city, zoom in close, use heat sensors and infrared.
Why Drones Make Us Nervous | Josh Dzieza | May 17, 2013 | THE DAILY BEAST
Helicopters equipped with infrared equipment flew over the area.
Rogue Ex-Cop Disappears in the Snow | Christine Pelisek | February 8, 2013 | THE DAILY BEAST
It was an air-view of the city of Zurb—taken, the high priest explained, by infrared light from an airboat over the city at night.
Temple Trouble | Henry Beam Piper
It boils liquid metal and cooks out energy from the infrared right through to hard radiation.
The K-Factor | Harry Harrison (AKA Henry Maxwell Dempsey)
Anyone leaving their Buggy would interrupt an infrared beam and stop the ride system.
Down and Out in the Magic Kingdom | Cory Doctorow
The film registers whatever the infrared searchlight illuminates.
Smugglers' Reef | John Blaine
Thanks to the goggles, both of them could see the normally invisible beams of the infrared flashlight.
Out Like a Light | Gordon Randall Garrett

British Dictionary definitions for infrared

infrared

/ (ˌɪnfrəˈrɛd) /

noun

the part of the electromagnetic spectrum with a longer wavelength than light but a shorter wavelength than radio waves; radiation with wavelength between 0.8 micrometres and 1 millimetre

adjective

of, relating to, using, or consisting of radiation lying within the infrared: infrared radiation

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for infrared

infrared

[ ĭn′frə-rĕd′ ]

Relating to the invisible part of the electromagnetic spectrum with wavelengths longer than those of visible red light but shorter than those of microwaves. See more at electromagnetic spectrum.

a closer look

In 1800 the astronomer Sir William Herschel discovered infrared light while exploring the relationship between heat and light. Herschel used a prism to split a beam of sunlight into a spectrum and then placed a thermometer in each of the bands of light. When he placed the thermometer just outside the red band, where there was no visible color, the temperature rose, as if light were shining on the thermometer. Further experiment showed that this invisible radiation behaved like visible light in many ways; for example, it could be reflected by a mirror. Infrared radiation is simply electromagnetic radiation with a lower frequency than visible light, having longer wavelengths of 0.7 micrometer to 1 millimeter. Ultraviolet radiation, like infrared radiation, lies just outside the visible part of the spectrum, but with higher frequencies; some animals, such as bees, are capable of seeing such radiation. Both infrared and ultraviolet radiation are often referred to as forms of light, though they cannot be seen by human beings. Heat energy is often transferred in the form of infrared radiation, which is given off from an object as a result of molecular collisions within it. Molecules typically have a characteristic infrared absorption spectrum, and infrared spectroscopy is a common technique for identifying the molecular structure of substances. Astronomers similarly analyze the infrared radiation emitted by celestial bodies to determine their temperature and composition.

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