arse vs fundament

arse and fundament both are nouns.

Word	Noun	Adjective	Verb	Adverb
arse	Yes	No	No	No
fundament	Yes	No	No	No

As nouns, arse and fundament are synonyms defined as:

arse (noun)	fundament (noun)
vulgar slang for anus	lowest support of a structure
the fleshy part of the human body that you sit on	the fleshy part of the human body that you sit on
	the fundamental assumptions from which something is begun or developed or calculated or explained