achromatic vs chromaticity

achromatic is not a noun while chromaticity is a noun.

Word	Noun	Adjective	Verb	Adverb
achromatic	No	Yes	No	No
chromaticity	Yes	No	No	No

achromatic (noun)	chromaticity (noun)
	the quality of a color as determined by its dominant wavelength

achromatic (adjective)	chromaticity (adjective)
having no hue