What does "appurtenance" mean?

Appurtenance: 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. Tomlins. Bouvier. Burrill. Globes . . . provided as appurtenances to astronomy. Bacon. The structure of the eye, and of its appurtenances. Reid.