chromaticity vs achromatic

chromaticity is a noun but achromatic is not a noun.

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

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

chromaticity (adjective)	achromatic (adjective)
	having no hue