arbitrariness vs whimsy

arbitrariness and whimsy both are nouns.

Word	Noun	Adjective	Verb	Adverb
arbitrariness	Yes	No	No	No
whimsy	Yes	No	No	No

As nouns, arbitrariness and whimsy are synonyms defined as:

arbitrariness and whimsy: the trait of acting unpredictably and more from whim or caprice than from reason or judgment

Other synonyms of arbitrariness include capriciousness, flightiness, whimsey, whimsicality.

arbitrariness (noun)	whimsy (noun)
the trait of acting unpredictably and more from whim or caprice than from reason or judgment	the trait of acting unpredictably and more from whim or caprice than from reason or judgment
	an odd or fanciful or capricious idea