yak's milk vs milk

yak's milk and milk both are nouns.

Word	Noun	Adjective	Verb	Adverb
yak's milk	Yes	No	No	No
milk	Yes	No	Yes	No

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

yak's milk: the milk of a yak
milk: a white nutritious liquid secreted by mammals and used as food by human beings

yak's milk (noun)	milk (noun)
the milk of a yak	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

yak's milk (verb)	milk (verb)
	take milk from female mammals
	add milk to
	exploit as much as possible