additive vs extra

additive and extra both are nouns.

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

additive (noun)	extra (noun)
something added to enhance food or gasoline or paint or medicine	something additional of the same kind
	an additional edition of a newspaper (usually to report a crisis)
	a minor actor in crowd scenes

additive (adjective)	extra (adjective)
characterized or produced by addition	further or added
designating or involving an equation whose terms are of the first degree	more than is needed, desired, or required
	added to a regular schedule

additive (adverb)	extra (adverb)
	unusually or exceptionally