roundness vs buxomness

roundness and buxomness both are nouns.

Word	Noun	Adjective	Verb	Adverb
roundness	Yes	No	No	No
buxomness	Yes	No	No	No

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

roundness: the bodily property of being well rounded
buxomness: the bodily property of being attractively plump and vigorous and (of women) full-bosomed

Other hyponyms of roundness include chubbiness, pudginess, rolypoliness, tubbiness.

roundness (noun)	buxomness (noun)
the property possessed by a line or surface that is curved and not angular	the bodily property of being attractively plump and vigorous and (of women) full-bosomed
the bodily property of being well rounded
the quality of being round numbers
the fullness of a tone of voice