Pharmacology is a branch of pharmaceutical sciences concerned with the study of drug or medication action. It is a study of how a drug or chemical substance exerts biochemical or physiological  effect on the cell, tissue organ or organism.

Pharmacology is a division of pharmaceutical sciences that is concerned with the study of action of chemical substances or drugs on human body. A drug can be defined as any artificial or natural, or endogenous molecule which exerts a biochemical or physiological effect on the cell, tissue, organ, or organism. Pharmacology is the study of action of drug on biological system and response of body to the drug or chemical substance. The discipline covers the sources, chemical properties, biological effects, and therapeutic uses of drugs.