preconceived idea vs prepossession

preconceived idea and prepossession both are nouns.

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

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

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

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

preconceived idea (noun)	prepossession (noun)
an opinion formed beforehand without adequate evidence	an opinion formed beforehand without adequate evidence
	the condition of being prepossessed