the state of relying on or being controlled by someone or something else
"The country's heavy reliance on imported oil created a dangerous economic dependency that left it vulnerable to global market fluctuations."
being abnormally tolerant to and dependent on something that is psychologically or physically habit-forming (especially alcohol or narcotic drugs)
"After years of heavy drinking, his severe dependency meant he could not function without a daily dose of alcohol."
a geographical area politically controlled by a distant country
"The island nation became a colonial dependency of the British Empire in the 19th century."
A state of dependence; a refusal to exercise initiative.
"His constant reliance on others revealed a dangerous dependency that prevented him from making any decisions without permission."
In plain English: A dependency is when you need something else to exist or work properly on its own.
"The country's economy became dependent on exports, creating a dangerous financial dependency for everyone there."
Usage: Use dependency to describe a situation where one person, system, or thing relies on another for support or function. Avoid confusing it with independence when discussing the need for external assistance versus self-sufficiency.
The word dependency comes from combining the root depend with suffixes like -cy or -y to form a noun. It originally described the state of relying on something else and entered English through these standard word-building processes.