boundary vs maximum

boundary and maximum both are nouns.

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

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

boundary (noun)	maximum (noun)
the greatest possible degree of something	the greatest possible degree
the line or plane indicating the limit or extent of something	the point on a curve where the tangent changes from positive on the left to negative on the right
a line determining the limits of an area	the largest possible quantity

boundary (adjective)	maximum (adjective)
	the greatest or most complete or best possible