standdown vs stoppage

standdown and stoppage both are nouns.

Word	Noun	Adjective	Verb	Adverb
standdown	Yes	No	No	No
stoppage	Yes	No	No	No

As nouns, stoppage is a hypernym of standdown; that is, stoppage is a word with a broader meaning than standdown:

Other hypernyms of standdown include stop.

standdown (noun)	stoppage (noun)
(military) a temporary stop of offensive military action	the act of stopping something
a suspension and relaxation from an alert state or a state of readiness	an obstruction in a pipe or tube
	the state of inactivity following an interruption