synovium vs synovial membrane

synovium and synovial membrane both are nouns.

Word	Noun	Adjective	Verb	Adverb
synovium	Yes	No	No	No
synovial membrane	Yes	No	No	No

As nouns, synovium and synovial membrane are synonyms defined as:

synovium and synovial membrane: a thin membrane in synovial (freely moving) joints that lines the joint capsule and secretes synovial fluid

synovium (noun)	synovial membrane (noun)
a thin membrane in synovial (freely moving) joints that lines the joint capsule and secretes synovial fluid	a thin membrane in synovial (freely moving) joints that lines the joint capsule and secretes synovial fluid