milk vs sustenance

milk and sustenance both are nouns.

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

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

milk (noun)	sustenance (noun)
produced by mammary glands of female mammals for feeding their young	the act of sustaining life by food or providing a means of subsistence
a white nutritious liquid secreted by mammals and used as food by human beings	a source of materials to nourish the body
any of several nutritive milklike liquids	the financial means whereby one lives

milk (verb)	sustenance (verb)
take milk from female mammals
add milk to
exploit as much as possible