Generic name of a common drug?

Trade name for drug is Pharmacology. There are many terms where drug is referred to:

1. pharmacology - A medicine to treat an illness and give relief for a symptom.
2. pharmacology - Its an addiction, which affects especially our central nervous system.
3. pharmacology - It can also be a chemical or substance that is not related to medical treatment, but controls the way our mind and body works.
4. pharmacology - A substance or herbs or plants that is treated illegal and harmful to the human body or used for the purpose of temporary mental satisfaction and pleasure like marijuana

A Trade name is nothing but a Brand name under which a drug is marketed . No generic may be sold for a period of time under which the company who holds a patent still has the patent in force. This is to give the company of origin time to recoup their investments from Research & Development, testing, and initial maketing.