The Collaborative International Dictionary of English v.0.48:

Dependency \De*pend"en*cy\, n.; pl. Dependencies.
   1. State of being dependent; dependence; state of being
      subordinate; subordination; concatenation; connection;
      reliance; trust.
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            Any long series of action, the parts of which have
            very much dependency each on the other. --Sir J.
                                                  Reynolds.
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            So that they may acknowledge their dependency on the
            crown of England.                     --Bacon.
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   2. A thing hanging down; a dependence.
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   3. That which is attached to something else as its
      consequence, subordinate, satellite, and the like.
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            This earth and its dependencies.      --T. Burnet.
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            Modes I call such complex ideas which . . . are
            considered as dependencies on or affections of
            substances.                           --Locke.
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   4. A territory remote from the kingdom or state to which it
      belongs, but subject to its dominion; a colony; as, Great
      Britain has its dependencies in Asia, Africa, and America.
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   Note: Dependence is more used in the abstract, and dependency
         in the concrete. The latter is usually restricted in
         meaning to 3 and 4.
         [1913 Webster]

WordNet (r) 3.0 (2006):

dependency
    n 1: the state of relying on or being controlled by someone or
         something else [syn: dependence, dependance,
         dependency]
    2: being abnormally tolerant to and dependent on something that
       is psychologically or physically habit-forming (especially
       alcohol or narcotic drugs) [syn: addiction, dependence,
       dependance, dependency, habituation]
    3: a geographical area politically controlled by a distant
       country [syn: colony, dependency]