sour milk vs milk

sour milk and milk both are nouns.

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

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

sour milk: milk that has turned sour
milk: a white nutritious liquid secreted by mammals and used as food by human beings

sour milk (noun)	milk (noun)
milk that has turned sour	produced by mammary glands of female mammals for feeding their young
	a white nutritious liquid secreted by mammals and used as food by human beings
	any of several nutritive milklike liquids

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