life expectancy definition
Life expectancy is defined statistically as the average number of years remaining for an individual or a group of people at a given age.Longevity refers to the characteristics of the relatively long life span of some members of a population.athematically, life expectancy is the mean number of years of life remaining at a given age, assuming constant mortality rates. It is denoted by, which means the average number of subsequent years of life for someone now aged, according to a particular mortality experience.