string theory vs high-energy physics

string theory and high-energy physics both are nouns.

Word	Noun	Adjective	Verb	Adverb
string theory	Yes	No	No	No
high-energy physics	Yes	No	No	No

string theory (noun)	high-energy physics (noun)
(particle physics) a theory that postulates that subatomic particles are one-dimensional strings	the branch of physics that studies subatomic particles and their interactions