acetabulum vs acetabular

acetabulum is a noun but acetabular is not a noun.

Word	Noun	Adjective	Verb	Adverb
acetabulum	Yes	No	No	No
acetabular	No	Yes	No	No

acetabulum (noun)	acetabular (noun)
the cup-shaped hollow in the hipbone into which the head of the femur fits to form a ball-and-socket joint

acetabulum (adjective)	acetabular (adjective)
	of the cup-shaped socket that receives the head of the thigh bone