Drugs

A drug is a chemical substance that has biological effects on humans.

Drugs are used in pharmacology for cure or treatment.

Recreational drugs are chemical substances that are not used for medical purposes, but only for pleasure.

Drugs cause addiction and habituation, and cause side effects. Many drugs are illegal.

Drugs can be:
-inhaled, like an aerosol or a powder; 
-injected, like heroin;
-insuflated into the nose, like cocain. 

pills: the pills drugs are very extended in some  people,  LSD.