additive

(mathematics) Pertaining to addition; that can be, or has been, added.

(mathematics, of a function, etc.) That is distributive over addition.

(group theory, of a group, semigroup, etc.) Whose operator is identified as addition.

(chemistry) Pertaining to chemical addition.

(genetics) 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.