fundament vs explanation

fundament and explanation both are nouns.

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

fundament (noun)	explanation (noun)
lowest support of a structure	thought that makes something comprehensible
the fleshy part of the human body that you sit on	a statement that makes something comprehensible by describing the relevant structure or operation or circumstances etc.
the fundamental assumptions from which something is begun or developed or calculated or explained	the act of explaining; making something plain or intelligible