nub vs bare bones

nub and bare bones both are nouns.

Word	Noun	Adjective	Verb	Adverb
nub	Yes	No	No	No
bare bones	Yes	No	No	No

As nouns, bare bones is a hyponym of nub; that is, bare bones is a word with a more specific, narrower meaning than nub:

nub: the choicest or most essential or most vital part of some idea or experience
bare bones: (plural) the most basic facts or elements

Other hyponyms of nub include hypostasis, haecceity, quiddity, quintessence, stuff.

nub (noun)	bare bones (noun)
the choicest or most essential or most vital part of some idea or experience	(plural) the most basic facts or elements
a small piece
a small lump or protuberance