1. add-on(n = noun.artifact) addition, improver - a component that is added to something to improve it; "the addition of a bathroom was a major improvement"; "the addition of cinnamon improved the flavor"
is a kind of component, constituent, element
has particulars: additive, afterthought, annex, annexe, extension, wing, attachment, elongation, extension
Derived form verb add on1
2. add-on(n = noun.artifact) accessory, appurtenance, supplement - a supplementary component that improves capability;
is a kind of component, constituent, element
has particulars: auto accessory, computer accessory, fitting, fixings, trimmings
Derived form verb add on2