drug addiction vs dependance

drug addiction and dependance both are nouns.

Word	Noun	Adjective	Verb	Adverb
drug addiction	Yes	No	No	No
dependance	Yes	No	No	No

As nouns, dependance is a hypernym of drug addiction; that is, dependance is a word with a broader meaning than drug addiction:

drug addiction: an addiction to a drug (especially a narcotic drug)
dependance: being abnormally tolerant to and dependent on something that is psychologically or physically habit-forming (especially alcohol or narcotic drugs)

Other hypernyms of drug addiction include addiction, dependence, dependency, habituation.

drug addiction (noun)	dependance (noun)
an addiction to a drug (especially a narcotic drug)	the state of relying on or being controlled by someone or something else
	being abnormally tolerant to and dependent on something that is psychologically or physically habit-forming (especially alcohol or narcotic drugs)