English Reference

Word

infrared

Phoneticsin·frared

US/ˌɪnfɹɝˈɛd/

UK/ˌɪnfɹəɹˈɛd/

Definitions

01invisible light/heat

B2 · Upper Intermediate Uncountable noun Science Technical

n. a type of light that you cannot see, but you can feel it as heat.

n. electromagnetic radiation with wavelengths between 700 nm and 1 mm, situated between the visible spectrum and microwaves.

“The snake can find its prey in the dark by sensing infrared.”

“The telescope captures infrared to peer through dense clouds of space dust that block our view of distant stars.”

Usage

Often used as an uncountable noun when referring to the radiation itself.

Synonyms

thermal radiation

Antonyms

02using infrared light

B2 · Upper Intermediate Science Technical

adj. describes technology or light that uses the infrared part of the spectrum.

adj. relating to or using electromagnetic radiation in the infrared spectrum.

“You can use an infrared remote to change the TV channel.”

“Security teams used infrared cameras to monitor the perimeter of the building during the blackout.”

Usage

This adjective is non-gradable; something cannot be 'more infrared' than something else.

Synonyms

Collocations

Common phrases and expressions where native English speakers use the word “infrared” in context.

01. infrared light

Real-World Examples

“In our experiments, the cover allowed more than 60% of visible light to pass through on average while reflecting more than 80% of infrared light back at the sun.”
Phys.org 26 Aug 2026
“All these telescopes had been outfitted with newly available infrared detectors.”
The Conversation 27 Aug 2026

Etymology

From infra- + red.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Domain

Physics

This entry

Exam level
CambridgeCambridgeCambridge English QualificationsThe exam suite from Cambridge University Press & Assessment, from A1 Movers up to C2 Proficiency. The benchmark names double as CEFR labels.B2 FirstIELTSIELTSInternational English Language Testing SystemThe 0–9 band test co-owned by the British Council, IDP, and Cambridge. Used for university entry, work, and migration.5.5–6.5TOEFL iBTTOEFL iBTTest of English as a Foreign Language, Internet-Based TestETS's academic English test, the standard route for US university admissions. Scored 0–120, with a 1–6 scale since 2026.1–6 scale: 4.0–4.572–94TOEICTOEICTest of English for International CommunicationETS's workplace English test, big in Japan and Korea. Listening & Reading scores 10–990 and tops out at C1.785–944EikenEikenTest in Practical English ProficiencyThe English proficiency test from the Eiken Foundation of Japan, widely taken by Japanese students. Grades run from 5 to 1, with Pre-1 and Pre-2 between them.Pre-1
Frequency
Frequent
Level
B2 · Upper Intermediate
Updated

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English Reference