pile vs pile up

pile is a noun but pile up is not a noun.

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

pile (noun)	pile up (noun)
a nuclear reactor that uses controlled nuclear fission to generate energy
battery consisting of voltaic cells arranged in series; the earliest electric battery devised by Volta
the yarn (as in a rug or velvet or corduroy) that stands up from the weave
a column of wood or steel or concrete that is driven into the ground to provide support for a structure
fine soft dense hair (as the fine short hair of cattle or deer or the wool of sheep or the undercoat of certain dogs)
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)	pile up (verb)
arrange in stacks	increase in amount by collecting or gathering
place or lay as if in a pile	arrange into piles or stacks
press tightly together or cram	get or gather together