piles vs stacks

piles and stacks both are nouns.

Word	Noun	Adjective	Verb	Adverb
piles	Yes	No	No	No
stacks	Yes	No	No	No

As nouns, piles and stacks are synonyms defined as:

Other synonyms of piles include dozens, gobs, heaps, lashings, loads, lots, oodles, rafts, scads, scores, slews, tons, wads.

piles (noun)	stacks (noun)
a large number or amount	storage space in a library consisting of an extensive arrangement of bookshelves where most of the books are stored
venous swelling external or internal to the anal sphincter	a large number or amount