Health is a state of human body. In this state, no disease can be found, and its biological parameters are stable in the normal range of change, and it has good adaptability to the changes of external environment (nature and society) in the daily range.
There are many definitions of health, all of which have their basis and imperfections. The preface to the Constitution of the World Health Organization puts forward an authoritative definition: health is a state of complete physical, mental and social comfort, not just the absence of disease or weakness. Some people accuse it of being an unattainable "utopia" definition, or think that it is not a definition of health, but a social goal, or that it understands health from a sociological perspective.
In fact, no matter from which angle, health is a vague concept. No pain is of course the basic condition of health, but the concept of pain is not clearer than health. An allergic person is healthy from any point of view as long as he is not exposed to allergens, but if he is exposed to allergens, he will have a rash or asthma, even shock and even death. It is an improvement to define health by the degree of adaptation to the environment and to understand health by linking people with the environment.
But this definition focuses on the function of the human body, and it also has its problems. For example, a healthy professor may not be able to adapt to the physical labor of dock workers, both of which are carried out daily in society. It seems to be the most accurate and convenient to define health by biological parameters, because as long as you open medical textbooks, you can find the normal values in all aspects of the human body. However, athletes who are taller than ordinary people should be classified as unhealthy according to this standard.
In fact, these normal values are calculated by statistical methods after investigation from normal people, but their normal range does not include all normal people, only 95% of them are taken, that is, 2.5% above the upper limit and 2.5% below the lower limit, and normal people are not included.
Therefore, many clinicians believe that the name of "normal value" here is not in line with the actual situation and should be changed to "standard value" or "variation range" to avoid misunderstanding. The definition of health put forward in the preface of the Constitution of the World Health Organization has been recognized by most countries in the world, but "a state of complete physical, mental and social comfort" is a difficult standard to master.