Definition: "Dependance" (more commonly spelled "dependence") is a noun that refers to the state of needing someone or something for support or help. It can also mean relying on something in a way that might be unhealthy, such as relying on drugs or alcohol.
"Dependance" (or "dependence") describes a state of relying on someone or something else. It can refer to general reliance or more serious situations like addiction.