cavernous sinus vs sinus

cavernous sinus and sinus both are nouns.

Word	Noun	Adjective	Verb	Adverb
cavernous sinus	Yes	No	No	No
sinus	Yes	No	No	No

As nouns, sinus is a hypernym of cavernous sinus; that is, sinus is a word with a broader meaning than cavernous sinus:

cavernous sinus: either of a pair of large venous sinuses in the cranial cavity
sinus: a wide channel containing blood; does not have the coating of an ordinary blood vessel

Other hypernyms of cavernous sinus include venous sinus.

cavernous sinus (noun)	sinus (noun)
either of a pair of large venous sinuses in the cranial cavity	a wide channel containing blood; does not have the coating of an ordinary blood vessel
	any of various air-filled cavities especially in the bones of the skull
	an abnormal passage leading from a suppurating cavity to the body surface