part vs nub

part and nub both are nouns.

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

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

Other hyponyms of part include body part, corpus, acicula, base, corner, craton, cutting, fragment, hunk, lump, stub, segment, slice, strip, world.

part (noun)	nub (noun)
the actions and activities assigned to or required or expected of a person or group	the choicest or most essential or most vital part of some idea or experience
the effort contributed by a person in bringing about a result	a small piece
something less than the whole of a human artifact	a small lump or protuberance
an item that is an instance of some type
a line of scalp that can be seen when sections of hair are combed in opposite directions
one of the portions into which something is regarded as divided and which together constitute a whole
an actor's portrayal of someone in a play
that which concerns a person with regard to a particular role or situation
the melody carried by a particular voice or instrument in polyphonic music
the extended spatial location of something
a portion of a natural object
assets belonging to or due to or contributed by an individual person or group
something determined in relation to something that includes it

part (verb)	nub (verb)
move or break apart
force, take, or pull apart
depart for someplace
go one's own way; move apart
discontinue an association or relation; go different ways

part (adverb)	nub (adverb)
to some extent; in some degree; not wholly