rectus superior vs eye muscle

rectus superior and eye muscle both are nouns.

Word	Noun	Adjective	Verb	Adverb
rectus superior	Yes	No	No	No
eye muscle	Yes	No	No	No

As nouns, eye muscle is a hypernym of rectus superior; that is, eye muscle is a word with a broader meaning than rectus superior:

rectus superior: the ocular muscle whose contraction turns the eyeball upward and medially
eye muscle: one of the small muscles of the eye that serve to rotate the eyeball

Other hypernyms of rectus superior include ocular muscle.

rectus superior (noun)	eye muscle (noun)
the ocular muscle whose contraction turns the eyeball upward and medially	one of the small muscles of the eye that serve to rotate the eyeball