"Annuity": 1. A series of equal future periodic cash flows, starting at Time 1 and ending at a predetermined future Time n. 2. More generally, any series of future periodic cash flows, either equal in amount or growing at a fixed compound rate per period, starting at a future time or already in payment, and usually ending at a later future time. 3. Any financial arrangement in which a periodic income is paid to an individual, often as a pension. 4. An insurance contract purchased from a life assurance company that pays an income in exchange for a lump sum. There are many variations on such annuities, depending on the nature of the income stream.