kernel vs nub

kernel and nub both are nouns.

Word	Noun	Adjective	Verb	Adverb
kernel	Yes	No	No	No
nub	Yes	No	No	No

As nouns, kernel and nub are synonyms defined as:

kernel and nub: the choicest or most essential or most vital part of some idea or experience

kernel (noun)	nub (noun)
the choicest or most essential or most vital part of some idea or experience	the choicest or most essential or most vital part of some idea or experience
a single whole grain of a cereal	a small piece
the inner and usually edible part of a seed or grain or nut or fruit stone	a small lump or protuberance