fittingness vs suitableness

fittingness and suitableness both are nouns.

Word	Noun	Adjective	Verb	Adverb
fittingness	Yes	No	No	No
suitableness	Yes	No	No	No

As nouns, suitableness is a hypernym of fittingness; that is, suitableness is a word with a broader meaning than fittingness:

fittingness: the quality of being suitable
suitableness: the quality of having the properties that are right for a specific purpose

Other hypernyms of fittingness include suitability.

fittingness (noun)	suitableness (noun)
the quality of being suitable	the quality of having the properties that are right for a specific purpose