tons vs stacks

tons and stacks both are nouns.

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

As nouns, tons and stacks are synonyms defined as:

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

tons (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
	a large number or amount