evacuation vs drainage

evacuation and drainage both are nouns.

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

As nouns, drainage is a hyponym of evacuation; that is, drainage is a word with a more specific, narrower meaning than evacuation:

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

Other hyponyms of evacuation include drain.

evacuation (noun)	drainage (noun)
the act of removing the contents of something	emptying something accomplished by allowing liquid to run out of it
the act of evacuating; leaving a place in an orderly fashion; especially for protection
the bodily process of discharging waste matter