theory of games vs game theory

theory of games and game theory both are nouns.

Word	Noun	Adjective	Verb	Adverb
theory of games	Yes	No	No	No
game theory	Yes	No	No	No

As nouns, theory of games and game theory are synonyms defined as:

theory of games and game theory: (economics) a theory of competition stated in terms of gains and losses among opposing players

theory of games (noun)	game theory (noun)
(economics) a theory of competition stated in terms of gains and losses among opposing players	(economics) a theory of competition stated in terms of gains and losses among opposing players