Eternity (from Latin aeturnus, itself derived from aevum, "age, time"): 1: Originally, a long period of time subjectively perceived by the involved persons as unending. Expressions such as "eons" or "thousand years" have frequently been used as synonyms for such an "eternal" or "everlasting" period in this sense (►Thousand-Year Empire).
2: Existence without temporal beginning or end, or an existence outside of ►time altogether. The laws of logic and mathematics are often thought to be eternal in this sense. For Plato there is a difference between the everlastingness of the realm of phenomena, whose end or beginning cannot be conceived by us, and the eternal nature of the ideas, which are beyond all processes of coming into being and passing away.
An eternal period and an infinite period are not at all the same; since eternity does not have a beginning, it will also last longer than infinity. And yet, as the reader will find upon reading the section on ►cardinal numbers, an infinite and an eternal period contain exactly the same number of seconds, hours, days, years, and eons.