Pharmacology is the branch of biology concerned with the study of drug action, where a drug can be broadly defined as a man-made, natural, or endogenous molecule that exerts a biochemical or physiological effect on the cell, tissue, organ, or organism. Sometimes the word pharmacon is used as a term to encompass these endogenous and exogenous bioactive species. More specifically, it is the study of interaction that occurs between a living organism and chemicals that affect normal or abnormal biochemical function. The field encompasses drug composition and properties, synthesis and drug design, molecular and cellular mechanisms, signal transduction/cellular communication, molecular diagnostics, interactions, toxicology, chemical biology, therapy and medical application, and antipathogenic capabilities. The two main areas of pharmacology are pharmacokinetics and pharmacodynamics. It is a biomedical science deal with the research, discovery, and characterization of chemicals which show biological effects and elucidation of cellular and organismal function concerning these chemicals.
The discipline of pharmacology can be divided into many sub-disciplines each with a specific topic.