sustenance vs meal

sustenance and meal both are nouns.

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

As nouns, meal is a hyponym of sustenance; that is, meal is a word with a more specific, narrower meaning than sustenance:

sustenance (noun)	meal (noun)
the act of sustaining life by food or providing a means of subsistence	the food served and eaten at one time
a source of materials to nourish the body	coarsely ground foodstuff; especially seeds of various cereal grasses or pulse
the financial means whereby one lives	any of the occasions for eating food that occur by custom or habit at more or less fixed times