medial rectus vs eye muscle

medial rectus and eye muscle both are nouns.

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

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

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

Other hypernyms of medial rectus include ocular muscle.

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