rim vs boundary

rim and boundary both are nouns.

Word	Noun	Adjective	Verb	Adverb
rim	Yes	No	Yes	No
boundary	Yes	No	No	No

As nouns, boundary is a hypernym of rim; that is, boundary is a word with a broader meaning than rim:

Other hypernyms of rim include round shape, bound, edge.

rim (noun)	boundary (noun)
the top edge of a vessel or other container	the greatest possible degree of something
a projection used for strength or for attaching to another object	the line or plane indicating the limit or extent of something
the outer part of a wheel to which the tire is attached	a line determining the limits of an area
(basketball) the hoop from which the net is suspended
the shape of a raised edge of a more or less circular object