preconceived notion vs preconceived idea

preconceived notion and preconceived idea both are nouns.

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

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

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

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

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