Overview

Health is commonly defined as more than the absence of illness. The World Health Organization's widely cited formulation describes health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity." This definition emphasizes that health encompasses how bodies function, how people think and feel, and how they interact within their communities. For the original wording and historical context consult WHO sources.

Key dimensions

Three broad, interrelated dimensions are usually distinguished:

  • Physical health — the functioning of the body, fitness, absence of disease, and capacity to carry out daily activities. For practical guidelines about physical health, see resources on exercise and nutrition at physical health.
  • Mental health — emotional well-being, cognitive functioning, the capacity to manage stress, and resilience. Mental health is essential for thinking, learning, and relationships.
  • Social health — the quality of relationships, social support, and ability to participate in community life. Family, work, school, and friendships shape social health; more on social supports is available via social determinants.

Determinants and measurement

Health is influenced by a mix of biological, behavioral, environmental and social factors. Genetic predisposition, lifestyle choices (diet, activity, substance use), access to healthcare, education, housing, income and the physical environment all interact to affect health outcomes. Public health and clinical practice use a range of measures — such as life expectancy, quality-adjusted life years, morbidity rates, and self-reported well-being — to assess population and individual health.

History and development of the idea

The modern, holistic idea of health emerged in the 20th century as medicine broadened from treating disease to preventing illness and promoting well-being. International organizations and national public health systems helped popularize the multidimensional view of health, linking medical care with social policy, sanitation, workplace safety and health education.

Promotion, prevention and examples

Maintaining and improving health involves interventions at individual and societal levels. Typical strategies include:

  • Primary prevention — vaccination, healthy diets, physical activity, and safety measures to prevent disease before it occurs.
  • Secondary prevention — screening and early treatment to limit progression of disease.
  • Tertiary prevention — rehabilitation and measures to reduce complications and improve quality of life.

Examples: promoting active transport and green spaces to support physical activity; workplace programs and counseling to support mental health; social policies that reduce poverty to address social determinants.

Distinctions and notable points

Health is dynamic rather than static: people may live with chronic conditions yet experience high levels of well-being. Distinguish between illness (subjective experience) and disease (objective pathology), and between health care (medical services) and public health (population-level prevention and policy). Understanding these distinctions helps shape effective responses, from clinical care to community programs and policy interventions.