additive (n.) Look up additive at Dictionary.com
"something that is added" to a chemical solution or food product, 1945, from additive (adj.).
additive (adj.) Look up additive at Dictionary.com
1690s, "tending to be added," from Late Latin additivus "added, annexed," from past participle stem of Latin addere "add to, join, attach" (see addition). Alternative addititious "additive, additional" (1748) is from Latin additicius "additional."