preconceived opinion vs thought

preconceived opinion and thought both are nouns.

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

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

preconceived opinion: 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 opinion include opinion, persuasion, sentiment, view.

preconceived opinion (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