Health is the level of functional or
metabolic efficiency of a living
organism. In
humans it is the ability of individuals or communities to adapt and self-manage when facing physical, mental or social challenges. The
World Health Organization (WHO) defined health in its broader sense in its 1948 constitution as "a state of complete physical, mental, and social
well-being and not merely the absence of disease or infirmity." This definition has been subject to controversy, in particular as lacking operational value and because of the problem created by use of the word "complete" Other definitions have been proposed, among which a recent definition that correlates health and personal satisfaction. Classification systems such as the
WHO Family of International Classifications, including the
International Classification of Functioning, Disability and Health (ICF) and the
International Classification of Diseases (ICD), are commonly used to define and measure the components of health. Health is that balanced condition of the living organism in which the integral, harmonious performance of the vital functions tends to the preservation of the organism and the normal development of the individual.
