stacks vs piles

stacks and piles both are nouns.

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

As nouns, stacks and piles are synonyms defined as:

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

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