plainness vs chasteness

plainness and chasteness both are nouns.

Word	Noun	Adjective	Verb	Adverb
plainness	Yes	No	No	No
chasteness	Yes	No	No	No

As nouns, chasteness is a hyponym of plainness; that is, chasteness is a word with a more specific, narrower meaning than plainness:

Other hyponyms of plainness include restraint, simpleness, simplicity, austereness, severeness, severity, bareness, starkness.

plainness (noun)	chasteness (noun)
the appearance of being plain and unpretentious	lack of ornamentation
an appearance that is not attractive or beautiful
clarity as a consequence of being perspicuous
the state of being unmixed with other material