cavernous sinus vs venous sinus

cavernous sinus and venous sinus both are nouns.

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

As nouns, venous sinus is a hypernym of cavernous sinus; that is, venous 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
venous sinus: a wide channel containing blood; does not have the coating of an ordinary blood vessel

Other hypernyms of cavernous sinus include sinus.

cavernous sinus (noun)	venous 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