meat and potatoes vs fundament

meat and potatoes and fundament both are nouns.

Word	Noun	Adjective	Verb	Adverb
meat and potatoes	Yes	No	No	No
fundament	Yes	No	No	No

As nouns, fundament is a hypernym of meat and potatoes; that is, fundament is a word with a broader meaning than meat and potatoes:

meat and potatoes: the fundamental part
fundament: the fundamental assumptions from which something is begun or developed or calculated or explained

Other hypernyms of meat and potatoes include base, basis, cornerstone, foundation, groundwork.

meat and potatoes (noun)	fundament (noun)
the fundamental part	lowest support of a structure
	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