opposition vs flip side

opposition and flip side both are nouns.

Word	Noun	Adjective	Verb	Adverb
opposition	Yes	No	No	No
flip side	Yes	No	No	No

As nouns, flip side is a hyponym of opposition; that is, flip side is a word with a more specific, narrower meaning than opposition:

opposition (noun)	flip side (noun)
the act of hostile groups opposing each other	a different aspect of something (especially the opposite aspect)
the action of opposing something that you disapprove or disagree with
a body of people united in opposing something
an armed adversary (especially a member of an opposing military force)
a contestant that you are matched against
a direction opposite to another
the relation between opposed entities