drainage vs voidance

drainage and voidance both are nouns.

Word	Noun	Adjective	Verb	Adverb
drainage	Yes	No	No	No
voidance	Yes	No	No	No

As nouns, voidance is a hypernym of drainage; that is, voidance is a word with a broader meaning than drainage:

drainage: emptying something accomplished by allowing liquid to run out of it
voidance: the act of removing the contents of something

Other hypernyms of drainage include emptying, evacuation.

drainage (noun)	voidance (noun)
emptying something accomplished by allowing liquid to run out of it	the act of removing the contents of something