That which belongs to something else; an adjunct; an appendage; an accessory; something annexed to another thing more worthy; in common parlance and legal acceptation, something belonging to another thing as principal, and which passes as incident to it, as a right of way, or other easement to land; a right of common to pasture, an outhouse, barn, garden, or orchard, to a house or messuage. In a strict legal sense, land can never pass as an appurtenance to land.
Term for what belongs to and goes with something else
Accessory, Add-on, Supplement
Appurtenance in Spanish is Accesorio