A dependency describes a thing necessary for a program to compile or run. In general, dependencies are libraries that need to be linked (whether at compile-time or at run-time). Of course, some necessary tool (like yacc or lex) could also be a dependency.

De*pend"en*cy (?), n.; pl. Dependencies ().

1.

State of being dependent; dependence; state of being subordinate; subordination; concatenation; connection; reliance; trust.

Any long series of action, the parts of which have very much dependency each on the other. Sir J. Reynolds.

So that they may acknowledge their dependency on the crown of England. Bacon.

2.

A thing hanging down; a dependence.

3.

That which is attached to something else as its consequence, subordinate, satellite, and the like.

This earth and its dependencies. T. Burnet.

Modes I call such complex ideas which . . . are considered as dependencies on or affections of substances. Locke.

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.

⇒ Dependence is more used in the abstract, and dependency in the concrete. The latter is usually restricted in meaning to 3 and 4.

 

© Webster 1913.