heap vs tidy sum

heap and tidy sum both are nouns.

Word	Noun	Adjective	Verb	Adverb
heap	Yes	No	Yes	No
tidy sum	Yes	No	No	No

As nouns, heap and tidy sum are synonyms defined as:

heap and tidy sum: (often followed by `of') a large number or amount or extent

heap (noun)	tidy sum (noun)
a car that is old and unreliable	(often followed by `of') a large number or amount or extent
a collection of objects laid on top of each other
(often followed by `of') a large number or amount or extent