addition vs additive

addition and additive both are nouns.

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

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

Other hyponyms of addition include afterthought, annex, annexe, extension, wing, attachment, elongation, extension.

addition (noun)	additive (noun)
the arithmetic operation of summing; calculating the sum of two or more numbers	something added to enhance food or gasoline or paint or medicine
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

addition (adjective)	additive (adjective)
	characterized or produced by addition
	designating or involving an equation whose terms are of the first degree