starkness vs plainness

starkness and plainness both are nouns.

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

As nouns, plainness is a hypernym of starkness; that is, plainness is a word with a broader meaning than starkness:

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