Explanation:
A psychological disease in which a person becomes habituated in using a particular thing continuously is called addiction.
Drugs are chemical compounds which are often used to treat certain medical condition.
But these compounds are often very addictive and if a person develops an addiction towards it it causes ill effects on his mental, physical and social health. Such misuse of drugs is then called drug abuse. Drug abuse is a legal offence and a drug addict must seek for psychological and medical assistance to give up the addiction.