venous sinus vs duct

venous sinus and duct both are nouns.

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

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

venous sinus: a wide channel containing blood; does not have the coating of an ordinary blood vessel
duct: a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance

Other hypernyms of venous sinus include canal, channel, epithelial duct.

venous sinus (noun)	duct (noun)
a wide channel containing blood; does not have the coating of an ordinary blood vessel	an enclosed conduit for a fluid
	a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance
	a continuous tube formed by a row of elongated cells lacking intervening end walls