cogitation vs idea

cogitation and idea both are nouns.

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

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

Other hypernyms of cogitation include thought.

cogitation (noun)	idea (noun)
attentive consideration and meditation	the content of cognition; the main thing you are thinking about
a carefully considered thought about something	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