repast vs sustenance

repast and sustenance both are nouns.

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

As nouns, sustenance is a hypernym of repast; that is, sustenance is a word with a broader meaning than repast:

Other hypernyms of repast include aliment, alimentation, nourishment, nutriment, nutrition, victuals.

repast (noun)	sustenance (noun)
the food served and eaten at one time	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