sustenance vs sustainment

sustenance and sustainment both are nouns.

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

As nouns, sustenance and sustainment are synonyms defined as:

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

Other synonyms of sustenance include maintenance, sustentation, upkeep.

sustenance (noun)	sustainment (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