human elbow vs hinge joint

human elbow and hinge joint both are nouns.

Word	Noun	Adjective	Verb	Adverb
human elbow	Yes	No	No	No
hinge joint	Yes	No	No	No

As nouns, hinge joint is a hypernym of human elbow; that is, hinge joint is a word with a broader meaning than human elbow:

human elbow: hinge joint between the forearm and upper arm and the corresponding joint in the forelimb of a quadruped
hinge joint: a freely moving joint in which the bones are so articulated as to allow extensive movement in one plane

Other hypernyms of human elbow include ginglymoid joint, ginglymus.

human elbow (noun)	hinge joint (noun)
hinge joint between the forearm and upper arm and the corresponding joint in the forelimb of a quadruped	a joint allowing movement in one plane only
	a freely moving joint in which the bones are so articulated as to allow extensive movement in one plane