sustainment vs sustenance

sustainment and sustenance both are nouns.

Word	Noun	Adjective	Verb	Adverb
sustainment	Yes	No	No	No
sustenance	Yes	No	No	No

As nouns, sustainment and sustenance are synonyms defined as:

sustainment and sustenance: the act of sustaining life by food or providing a means of subsistence

Other synonyms of sustainment include maintenance, sustentation, upkeep.

sustainment (noun)	sustenance (noun)
the act of sustaining life by food or providing a means of subsistence	the act of sustaining life by food or providing a means of subsistence
	a source of materials to nourish the body
	the financial means whereby one lives