venous sinus vs epithelial duct

venous sinus and epithelial duct both are nouns.

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

As nouns, epithelial duct is a hypernym of venous sinus; that is, epithelial 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
epithelial 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, duct.

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