additive

Short definition from Wiktionary

Adjective

1. 1
   Pertaining to addition; that can be, or has been, added.
2. 2
   That is distributive over addition.
3. 3
   Whose operator is identified as addition.
4. 4
   Pertaining to chemical addition.
5. 5
   Of or pertaining to genes (or the interaction etc. of such genes) which govern the same trait and whose effects work together on the phenotype.

Noun

1. 1
   A substance added to another substance or product to produce specific properties in the combined substance.
2. 2
   A word or phrase that adds something, such as also, even, or nor.