preconceived idea vs thought

preconceived idea and thought both are nouns.

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

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

preconceived idea: an opinion formed beforehand without adequate evidence
thought: a personal belief or judgment that is not founded on proof or certainty

Other hypernyms of preconceived idea include opinion, persuasion, sentiment, view.

preconceived idea (noun)	thought (noun)
an opinion formed beforehand without adequate evidence	the process of using your mind to consider something carefully
	the content of cognition; the main thing you are thinking about
	the organized beliefs of a period or group or individual
	a personal belief or judgment that is not founded on proof or certainty