hinge joint vs synovial joint

hinge joint and synovial joint both are nouns.

Word	Noun	Adjective	Verb	Adverb
hinge joint	Yes	No	No	No
synovial joint	Yes	No	No	No

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

hinge joint: a freely moving joint in which the bones are so articulated as to allow extensive movement in one plane
synovial joint: a joint so articulated as to move freely

Other hypernyms of hinge joint include articulatio synovialis, diarthrosis.

hinge joint (noun)	synovial joint (noun)
a joint allowing movement in one plane only	a joint so articulated as to move freely
a freely moving joint in which the bones are so articulated as to allow extensive movement in one plane