infrared vs infrared spectrum

infrared and infrared spectrum both are nouns.

Word	Noun	Adjective	Verb	Adverb
infrared	Yes	Yes	No	No
infrared spectrum	Yes	No	No	No

infrared (noun)	infrared spectrum (noun)
the infrared region of the electromagnetic spectrum; electromagnetic wave frequencies below the visible range	the spectrum of infrared radiation
electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves

infrared (adjective)	infrared spectrum (adjective)
having or employing wavelengths longer than light but shorter than radio waves; lying outside the visible spectrum at its red end