Health is the level of functional and 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 changes.

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, the ambiguity in developing cohesive health strategies, 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.

Health care or healthcare is the maintenance or improvement of health via the diagnosis, treatment, and prevention of disease, illness, injury, and other physical and mental impairments in human beings.

Healthcare is delivered by health professionals (providers or practitioners) in allied health professions, chiropractic, physicians, physician associates, dentistry, midwifery, nursing, medicine, optometry, pharmacy, psychology, and other health professions.

It includes the work done in providing primary care, secondary care, and tertiary care, as well as in public health.

A patient is any recipient of health care services.

The patient is most often ill or injured and in need of treatment by a advanced practice registered nurse, physiotherapist, physician, physician assistant, psychologist, podiatrist, veterinarian, or other health care provider.

A community is a small or large social unit (a group of people) who have something in common, such as norms, religion, values, or identity.

Often - but not always - communities share a sense of place that is situated in a given geographical area (e.g. a country, village, town, or neighborhood).

Durable relations that extend beyond immediate genealogical ties also define a sense of community.

People tend to define those social ties as important to their identity, practice, and roles in social institutions like family, home, work, government, society, or humanity, at large.

Although communities are usually small relative to personal social ties (micro-level), "community" may also refer to large group affiliations (or macro-level), such as national communities, international communities, and virtual communities.