synovial joint vs articulatio

synovial joint and articulatio both are nouns.

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

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

synovial joint: a joint so articulated as to move freely
articulatio: (anatomy) the point of connection between two bones or elements of a skeleton (especially if it allows motion)

Other hypernyms of synovial joint include articulation, joint.

synovial joint (noun)	articulatio (noun)
a joint so articulated as to move freely	(anatomy) the point of connection between two bones or elements of a skeleton (especially if it allows motion)