pile vs stack

pile and stack both are nouns.

Word	Noun	Adjective	Verb	Adverb
pile	Yes	No	Yes	No
stack	Yes	No	Yes	No

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

As nouns, pile and stack are synonyms defined as:

pile and stack: (often followed by `of') a large number or amount or extent

As verbs, pile and stack are synonyms defined as:

Other synonyms of pile include heap.

pile (noun)	stack (noun)
a nuclear reactor that uses controlled nuclear fission to generate energy	a large tall chimney through which combustion gases and smoke can be evacuated
battery consisting of voltaic cells arranged in series; the earliest electric battery devised by Volta	a storage device that handles data so that the next item to be retrieved is the item most recently stored (LIFO)
the yarn (as in a rug or velvet or corduroy) that stands up from the weave	a list in which the next item to be removed is the item most recently stored (LIFO)
a column of wood or steel or concrete that is driven into the ground to provide support for a structure	an orderly pile
fine soft dense hair (as the fine short hair of cattle or deer or the wool of sheep or the undercoat of certain dogs)	(often followed by `of') a large number or amount or extent
a collection of objects laid on top of each other
a large sum of money (especially as pay or profit)
(often followed by `of') a large number or amount or extent

pile (verb)	stack (verb)
arrange in stacks	arrange in stacks
place or lay as if in a pile	load or cover with stacks
press tightly together or cram	arrange the order of so as to increase one's winning chances