whim vs idea

whim and idea both are nouns.

Word	Noun	Adjective	Verb	Adverb
whim	Yes	No	No	No
idea	Yes	No	No	No

As nouns, idea is a hypernym of whim; that is, idea is a word with a broader meaning than whim:

Other hypernyms of whim include thought.

whim (noun)	idea (noun)
an odd or fanciful or capricious idea	the content of cognition; the main thing you are thinking about
a sudden desire	your intention; what you intend to do
	an approximate calculation of quantity or degree or worth
	a personal view
	(music) melodic subject of a musical composition