ap·pur·te·nance /əˈpɝtnən(t)s, ˈpɚ/
 附屬物,附件
 Ap·pur·te·nance n.  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.
    Globes . . . provided as appurtenances to astronomy.   --Bacon.
    The structure of the eye, and of its appurtenances.   --Reid.
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 appurtenance
      n : a supplementary component that improves capability [syn: accessory,
           supplement, add-on]