A subordinate or supplementary item; an adjunct.
The definition of an appurtenance is something goes with or attaches to something else.
A thing or part added; increase; specif., a room or rooms added to a building
Affix means to create an addition to something.
Find another word for add-on. In this page you can discover 22 synonyms, antonyms, idiomatic expressions, and related words for add-on, like: accessory, appurtenance, supplement, addition, improver, append, affix, auto update, uninstaller, addons and v2-5.