tentorial sinus vs venous sinus

tentorial sinus and venous sinus both are nouns.

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

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

tentorial sinus: an unpaired sinus of the dura mater
venous sinus: a wide channel containing blood; does not have the coating of an ordinary blood vessel

Other hypernyms of tentorial sinus include sinus.

tentorial sinus (noun)	venous sinus (noun)
an unpaired sinus of the dura mater	a wide channel containing blood; does not have the coating of an ordinary blood vessel