explanation vs fundament

explanation and fundament both are nouns.

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

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