Drug abuse is where people use drugs way too much. When people receive medicinal drugs from a doctor, they grow addicted to that drug and won't give up on it. When the doctor ask's about the drug, the user tells the doctor that there still sick and they still need that drug when they don't. Drug abuse is something that would probably kill you if you abuse the drug too much. Never abuse drugs too much.
Reason you shouldn't abuse drugs is because it's bad for you and it could really hurt you in some way. Drug abuse can lead to some unknown disease or cancer or even worse. Why people abuse drugs is so they feel good about them selves or they became addicted to it. That's why you should not abuse drugs.