fundament

Backside is a related term of fundament.

As nouns the difference between backside and fundament

is that backside is the side of something that is opposite the front while fundament is foundation.

Rump is a related term of fundament.

As nouns the difference between rump and fundament

is that rump is the hindquarters of an animal while fundament is foundation.

Fundament is a related term of bum.

As nouns the difference between fundament and bum

is that fundament is foundation while bum is the buttocks or bum can be (north america|colloquial) a hobo; a homeless person, usually a man or bum can be (dated) a humming noise or bum can be (obsolete) a bumbailiff.

As a verb bum is

(uk|transitive|colloquial) to sodomize; to engage in anal sex or bum can be (colloquial) to ask someone to give one (something) for free; to beg for something or bum can be to depress; to make unhappy or bum can be to make a murmuring or humming sound.

As an interjection bum is

(label) an expression of annoyance.

As an adjective bum is

of poor quality or highly undesirable .

As nouns the difference between taxonomy and fundament

is that taxonomy is the science or the technique used to make a classification while fundament is foundation.