| Subject | English | Estonian |
| IT | addition class mark | lisaindeks (indekseeritava dokumendi kõrvalteemat tähistav indeks (Vrd. põhiindeks)) |
| IT | addition class number | lisaindeks (indekseeritava dokumendi kõrvalteemat tähistav indeks (Vrd. põhiindeks)) |
| IT | addition classification mark | lisaindeks (indekseeritava dokumendi kõrvalteemat tähistav indeks (Vrd. põhiindeks)) |
| IT | addition classification number | lisaindeks (indekseeritava dokumendi kõrvalteemat tähistav indeks (Vrd. põhiindeks)) |
| math. | addition of variates | muutujate liitmine |
| comp., MS | addition operator | liitmismärk (The + character, used to indicate addition or a positive number) |
| environ. | addition polymer A polymer formed by the chain addition of unsaturated monomer molecules, such as olefins, with one another without the formation of a by-product, as water; examples are polyethylene, polypropylene and polystyrene | ahelpolümeer |
| environ. | chemical addition Chemical reaction in which one or more of the double bonds or triple bonds in an unsaturated compound is converted to a single bond by the addition of other atoms or groups | liitumisreaktsioon |
| comp., MS | fixed asset addition | põhivara osa (An add-on item to a fixed asset that is considered part of the fixed asset and is not tracked as its own fixed asset, such as an extra battery for a laptop. Typically, an add-on item is maintenance or an improvement and relates to a write-up adjustment) |
| econ. | income in addition to normal pay | mittepalgaline sissetulek |