shack vs shelter

shack and shelter both are nouns.

Word	Noun	Adjective	Verb	Adverb
shack	Yes	No	Yes	No
shelter	Yes	No	Yes	No

As nouns, shelter is a hypernym of shack; that is, shelter is a word with a broader meaning than shack:

shack (noun)	shelter (noun)
small crude shelter used as a dwelling	a structure that provides privacy and protection from danger
	protective covering that provides protection from the weather
	temporary housing for homeless or displaced persons
	a way of organizing business to reduce the taxes it must pay on current earnings
	the condition of being protected

shack (verb)	shelter (verb)
move, proceed, or walk draggingly or slowly	invest (money) so that it is not taxable
make one's home in a particular place or community	provide shelter for