preconceived idea vs preconceived notion

preconceived idea and preconceived notion both are nouns.

Word	Noun	Adjective	Verb	Adverb
preconceived idea	Yes	No	No	No
preconceived notion	Yes	No	No	No

As nouns, preconceived idea and preconceived notion are synonyms defined as:

preconceived idea and preconceived notion: an opinion formed beforehand without adequate evidence

Other synonyms of preconceived idea include parti pris, preconceived opinion, preconception, prepossession.

preconceived idea (noun)	preconceived notion (noun)
an opinion formed beforehand without adequate evidence	an opinion formed beforehand without adequate evidence