Health is the ability of a biological system to acquire, convert, allocate, distribute, and utilize energy with maximum efficiency. The World Health Organization (WHO) defined human health in a 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", which makes it practically impossible to achieve. Other definitions have been proposed, among which a recent definition that correlates health and personal satisfaction.
In public relations and communication science, publics are groups of individual people, and the public (a.k.a. the general public) is the totality of such groupings. This is a different concept to the sociological concept of the Öffentlichkeit or public sphere. The concept of a public has also been defined in political science, psychology, marketing, and advertising. In public relations and communication science, it is one of the more ambiguous concepts in the field. Although it has definitions in the theory of the field that have been formulated from the early 20th century onwards, it has suffered in more recent years from being blurred, as a result of conflation of the idea of a public with the notions of audience, market segment, community, constituency, and stakeholder.
Public health is "the science and art of preventing disease, prolonging life and promoting human health through organized efforts and informed choices of society, organizations, public and private, communities and individuals." Analyzing the health of a population and the threats is the basis for public health. The "public" in question can be as small as a handful of people, an entire village or it can be as large as several continents, in the case of a pandemic. "Health" takes into account physical, mental and social well-being. It is not merely the absence of disease or infirmity, according to the World Health Organization. Public health is interdisciplinary. For example, epidemiology, biostatistics and health services are all relevant. Environmental health, community health, behavioral health, health economics, public policy, mental health and occupational safety, gender issues in health, sexual and reproductive health are other important subfields.
There are three wicks you know to the lamp of a man's life: brain, blood, and breath. Press the brain a little, its light goes out, followed by both the others. Stop the heart a minute, and out go all three of the wicks. Choke the air out of the lungs, and presently the fluid ceases to supply the other centres of flame, and all is soon stagnation, cold, and darkness.
Oliver Wendell Holmes, Sr., The Professor at the Breakfast Table (1859), XI.
With your talents and industry, with science, and that stedfast honesty which eternally pursues right, regardless of consequences, you may promise yourself every thing—but health, without which there is no happiness. An attention to health then should take place of every other object. The time necessary to secure this by active exercises, should be devoted to it in preference to every other pursuit.
Thomas Jefferson, letter to Thomas Mann Randolph, Jr. (July 6, 1787); in Julian P. Boyd, ed., The Papers of Thomas Jefferson (1955), vol. 11, p. 558.
If a man is in health, he doesn't need to take anybody else's temperature to know where he is going.
E. B. White, in a letter to the New York Herald Tribune (29 November 1947).