is the expected (in the statistical sense) number of years of life remaining at a given age. It is denoted by , which means the average number of subsequent years of life for someone now aged
, according to a particular experience. Because life expectancy is an average, a particular person may well die many years before or many years after their "expected" survival. The term "maximum life span" has a quite different meaning. The "median life span" is also a different concept although fairly similar to life expectancy numerically in most developed countries.