- Adjective. (mathematics) Pertaining to addition; that can be, or has been, added.
- Adjective. (mathematics, of a function, etc.) Distributive over addition.
- Adjective. (algebra) Having addition as an operator. .
- Adjective. (chemistry) Pertaining to chemical addition.
- Adjective. (genetics) Describing genes (or the interaction etc. of such genes) which govern the same trait and whose effects work together on the phenotype.
- Noun. A substance added to another substance or product for its ability to alter its properties.