Einstein's theory of relativity vs relativity theory

Einstein's theory of relativity and relativity theory both are nouns.

Word	Noun	Adjective	Verb	Adverb
Einstein's theory of relativity	Yes	No	No	No
relativity theory	Yes	No	No	No

As nouns, Einstein's theory of relativity and relativity theory are synonyms defined as:

Einstein's theory of relativity and relativity theory: (physics) the theory that space and time are relative concepts rather than absolute concepts

Other synonyms of Einstein's theory of relativity include relativity, theory of relativity.

Einstein's theory of relativity (noun)	relativity theory (noun)
(physics) the theory that space and time are relative concepts rather than absolute concepts	(physics) the theory that space and time are relative concepts rather than absolute concepts