According to the constitution of the World Health Organization (WHO), health is "a state of complete physical, mental and social well-being, and does not consist only of the absence of disease or infirmity" and represents " one of the fundamental rights of every human being, whatever his race, religion, political opinions, economic or social condition ".

This definition, included in the preamble of the WHO constitution in 1946, has not been changed since. It involves the satisfaction of all the basic needs of the person, whether they are emotional, health, nutritional, social or cultural.

Human life expectancy is one of the most widely used statistical indicators in the field of forecasting and demographic projections, and to assess the level of development and the human development index of a State or a region of the world.

It makes it possible to quantify the mortality conditions in a given year: life expectancy at birth is equal to the average lifespan of a fictitious population which would live its entire existence under the mortality conditions of the year considered.

In demography, the mortality rate (or crude death rate) is the ratio between the annual number of deaths and the average total population over a period and in a given territory.

• WikipediA: Health
• WikipediA: Human life expectancy
• WikipediA: Mortality rate