Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
dependence, dependency (nn.)
Dependency has one specialized sense that it does not share with dependence: “a territory that is under the jurisdiction of another state,” as in Those three small islands are dependencies of Japan. Dependence means “the state of being dependent on,” as in His mother’s dependence on him for full support was well documented, or “addiction to,” as in phrases such as dependence on drugs or alcohol. But dependency is used in these senses too, as in drug dependency, although perhaps somewhat less frequently. In such uses the two words are synonyms, and Standard. See -CE.
