The word “longevity” is sometimes used synonymously with “life expectancy” in demography—especially when it concerns someone or something that lives longer than expected—however, the two words have slightly different definitions. In a similar vein to “discipline” and “precision,” “longevity” refers to the average number of years a human being lives, while “life expectancy” refers to the number of years the average population lives. This is illustrated by the fact that a large increase in life expectancy can be accompanied by a small increase in the overall longevity of the population. Speculations about longevity have gone beyond the recognition of the shortness of human lifespans, and have included consideration of ways to prolong life. The topic of longevity has been raised not only in the scientific community but also among travelers, science fiction writers, and utopian novelists. There are many difficulties in ascertaining the absolute longest human lifespan by contemporary standards, due to inaccurate or incomplete birth statistics. Novels, myths, and folklore have claimed past or future lifespans that are much longer than those proven by modern standards, and unconfirmed claims of longevity continue to abound, with talk of cases of longevity in the present.