1590s (adj.), 1610s (n.); see dependent + -cy. Originally also dependancy, on the French model, but the Latinate form gradually pushed this into disuse; see -ance. Meaning "territory subordinate to another nation" is recorded from 1680s.
1. In 1985, he began to show signs of alcohol and drug dependency.
2. Ukraine is handicapped by its near-total dependency on Russian oil.
3. We worried about his dependency on his mother.
4. Their aim is to reduce people's dependency on the welfare state.
5. Britain was a Roman dependency for a long period.