"infrared" in the noun sense
1. infrared, infrared frequency
the infrared region of the electromagnetic spectrum electromagnetic wave frequencies below the visible range
"they could sense radiation in the infrared"
2. infrared, infrared light, infrared radiation, infrared emission
electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves
"infrared" in the adjective sense
having or employing wavelengths longer than light but shorter than radio waves lying outside the visible spectrum at its red end
Source: WordNet® (An amazing lexical database of English)
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