sustentation vs sustainment

sustentation and sustainment both are nouns.

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

As nouns, sustentation and sustainment are synonyms defined as:

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

Other synonyms of sustentation include maintenance, sustenance, upkeep.

sustentation (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