thought vs mainstream

thought and mainstream both are nouns.

Word	Noun	Adjective	Verb	Adverb
thought	Yes	No	No	No
mainstream	Yes	No	No	No

As nouns, mainstream is a hyponym of thought; that is, mainstream is a word with a more specific, narrower meaning than thought:

thought (noun)	mainstream (noun)
the process of using your mind to consider something carefully	the prevailing current of thought
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