annex vs addition

annex and addition both are nouns.

Word	Noun	Adjective	Verb	Adverb
annex	Yes	No	Yes	No
addition	Yes	No	No	No

As nouns, addition is a hypernym of annex; that is, addition is a word with a broader meaning than annex:

Other hypernyms of annex include add-on, improver.

annex (noun)	addition (noun)
an addition that extends a main building	the arithmetic operation of summing; calculating the sum of two or more numbers
	the act of adding one thing to another
	a component that is added to something to improve it
	a suburban area laid out in streets and lots for a future residential area
	something added to what you already have
	a quantity that is added

annex (verb)	addition (verb)
add an extra part to
take (territory) as if by conquest