An Annuity is a series of cash flows (payments) received at regular intervals.
Other types of annuities
Ordinary Annuity. A series of equal payments made at the end of equal time periods. An ordinary annuity is assumed when using the compound interest tables. A Level Annuity and a Straight-line Annuity is the same as an ordinary annuity.
Annuity in Advance. A series of equal payments made at the beginning of equal time periods.
Other types of annuities (undefined in this glossary):
Constant Ratio Annuity
Reverse Annuity Mortgage