Health is the general condition of a person in all aspects. It is also a level of functional and/or metabolic efficiency of an organism, often implicitly human.
At the time of the creation of the World Health Organization (WHO), in 1948, health was defined as "a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity".
Only a handful of publications have focused specifically on the definition of health and its evolution in the first 6 decades. Some of them highlight its lack of operational value and the problem created by use of the word "complete." Others declare the definition, which has not been modified since 1948, "simply a bad one." 
In 1986, the WHO, in the Ottawa Charter for Health Promotion, said that health is "a resource for everyday life, not the objective of living. Health is a positive concept emphasizing social and personal resources, as well as physical capacities." Classification systems such as the WHO Family of International Classifications (WHO-FIC), which is composed of the International Classification of Functioning, Disability, and Health (ICF) and the International Classification of Diseases (ICD) also define health.
Overall health is achieved through a combination of physical, mental, and social well-being, which, together is commonly referred to as the Health Triangle.
Determinants of health
The LaLonde report suggests that there are four general determinants of health including human biology, environment, lifestyle, and healthcare services. Thus, health is maintained and improved not only through the advancement and application of health science, but also through the efforts and intelligent lifestyle choices of the individual and society.
The Alameda County Study examines the relationship between lifestyle and health. It has found that people can improve their health via exercise, enough sleep, maintaining a healthy weight, limiting alcohol use, and avoiding smoking.
Studies show that in developed countries, the lack of neighborhood recreational space that includes the natural environment leads to lower levels of neighborhood satisfaction and higher levels of obesity; therefore, lower overall well being. Therefore, the positive psychological benefits of natural space in urban neighborhoods should be taken into account in public policy and land use.
According to the World Health Organization, the main determinants of health include the social and economic environment, the physical environment and the person's individual characteristics and behaviors. Generally, the context in which an individual lives is of great importance on his life quality and health status. The social and economic environment are key factors in determining the health status of individuals given the fact that higher education levels are linked with a higher standard of life as well as a higher income. Generally, people who finish higher education are more likely to get a better job and therefore are less prone to stress by comparing to individuals with low education levels.
The physical environment is perhaps the most important factor that should be considered when classifying the health status of an individual. This includes factors such as clean water and air, safe houses, communities and roads all contribute to good health.
Genetics are also part of the system based on which the health of the population can be established. Genetics are closely related to the habits and behaviors individuals develop during their life, particularly in terms of lifestyle choices. For instance, people who come from families whose members had a more active lifestyle and followed healthier diets, non-smoking and non-drinking are more likely to follow the same pattern in their life. The example set by the family as well as the relationship with friends and family can have a great impact on one's general health. Nonetheless, genetics may play a role in the manner in which people cope with stress.
Moreover, the World Health Organization lists a wide range of other factors that can influence the well being of a person. According to WHO, the gender, social support networks and health services in terms of both quality and access to them are to be considered as health determinants. Access to health care is one of the large issues of the nowadays society, maybe even greater than the quality of the service. Individuals in developing countries are more prone to suffer from different health conditions because their access to the health care system is restricted mostly from financial reasons.
Although many individuals are often criticized for not taking good care of their health based on the presumption that the mirror's of one's personality is one's health., it is now accepted that there are many factors that have a significant impact on one's health and which cannot be controlled.
Achieving and maintaining health is an ongoing process. Effective strategies for staying healthy and improving one's health include the following elements:
Personal health depends partially on one's active, passive, and assisted observations about their health in their everyday life. The information gleaned from such observations may be used to inform personal decisions and actions (e.g., "I feel tired in the morning so I am going to try sleeping on a different pillow"), as well as clinical decisions and treatment plans (e.g., a patient who notices his or her shoes are tighter than usual may be having exacerbation of left-sided heart failure, and may require diuretic medication to reduce fluid overload) for patients who share their observations with their health care providers.
Personal health depends partially on the social structure of one's life. The maintenance of strong social relationships is linked to good health conditions, longevity, productivity, and a positive attitude. This is because positive social interaction as viewed by the participant increases many chemical levels in the brain which are linked to personality and intelligence traits.
Volunteering also can lead to a healthy life. To be a volunteer, while gaining plenty of social benefits, people also take their mind off their own troubles. Volunteering could even add years of life. According to a university study, compared with people who did not volunteer, senior citizens who volunteered showed a 67% reduced risk of dying during a seven-year period.
Hygiene is the practice of keeping the body clean to prevent infection and illness, and the avoidance of contact with infectious agents. Hygiene practices include bathing, brushing and flossing teeth, washing hands especially before eating, washing food before it is eaten, cleaning food preparation utensils and surfaces before and after preparing meals, and many others. This may help prevent infection and illness. By cleaning the body, dead skin cells are washed away with the germs, reducing their chance of entering the body.
Prolonged psychological stress may negatively impact health, and has been cited as a factor in cognitive impairment with aging, depressive illness, and expression of disease.. Stress management is the application of methods to either reduce stress or increase tolerance to stress. Relaxation techniques are physical methods used to relieve stress. Psychological methods include cognitive therapy, meditation, and positive thinking which work by reducing response to stress. Improving relevant skills and abilities builds confidence, which also reduces the stress reaction to situations where those skills are applicable.
Reducing uncertainty, by increasing knowledge and experience related to stress-causing situations, has the same effect. Learning to cope with problems better, such as improving problem solving and time management skills, may also reduce stressful reaction to problems. Repeatedly facing an object of one's fears may also desensitize the fight-or-flight response with respect to that stimulus—e.g., facing bullies may reduce fear of bullies.
Health care  is the prevention, treatment, and management of illness and the preservation of mental and physical well being through the services offered by the medical, nursing, and allied health professions.
Workplace wellness programs
Workplace wellness programs are recognized by an increasingly large number of companies for their value in improving the health and well-being of their employees, and for increasing morale, loyalty, and productivity. Workplace wellness programs can include things like onsite fitness centers, health presentations, wellness newsletters, access to health coaching, tobacco cessation programs and training related to nutrition, weight and stress management. Other programs may include health risk assessments, health screenings and body mass index monitoring.
Wellness programs may also be found in such places neighborhood community centers and schools. These typically require participants to have a greater degree of commitment to themselves, as they are voluntary.
Public health is "the science and art of preventing disease, prolonging life and promoting health through the organised efforts and informed choices of society, organizations, public and private, communities and individuals." (Winslow, 1920) It is concerned with threats to the overall health of a community based on population health analysis. The population in question can be as small as a handful of people or as large as all the inhabitants of several continents (for instance, in the case of a pandemic). Public health has many sub-fields, but is typically divided into the categories of epidemiology, biostatistics and health services. Environmental, social and behavioral health, and occupational health, are also important fields in public health.
The focus of public health intervention is to prevent rather than treat a disease through surveillance of cases and the promotion of healthy behaviors. In addition to these activities, in many cases treating a disease can be vital to preventing it in others, such as during an outbreak of an infectious disease. Vaccination schedules and distribution of condoms are examples of public health measures.
Unlike clinical professionals, public health is more focused on entire populations rather than on individuals. Its aim is preventing from happening or re-occurring health problems by implementing educational programs, developing policies, administering services, and conducting research.
Public health also takes several actions to limit the health disparities between different areas of the country, continent or world. The great issue this system is trying to solve is the access of individuals to health care which has always been restricted for those who did not dispose of the necessary financial means. Other academic disciplines that are comprised by this field include maternal and child health, health services administration, global health, public health practice, public health policy and nutrition.
The great positive impact of public health programs is widely admitted. Because of the health policies and the actions public health professionals develop, the 20th century has registered a decrease of the mortality rates in infants and children and a constant increase in life expectancy. It is estimated that the life expectancy for Americans has increased by thirty years since 1900.
Role of science in health
Health science is the branch of science focused on health, and it includes many subdisciplines. There are two approaches to health science: the study and research of the human body and health-related issues to understand how humans (and animals) function, and the application of that knowledge to improve health and to prevent and cure diseases.
Health research builds primarily on the basic sciences of biology, chemistry, and physics as well as a variety of multidisciplinary fields (for example medical sociology). Some of the other primarily research-oriented fields that make exceptionally significant contributions to health science are biochemistry, epidemiology, and genetics.