In investment, an annuity is a series of payments made at equal intervals. Examples of annuities are regular deposits to a savings account, monthly home mortgage payments, monthly insurance payments and pension payments. Annuities can be classified by the frequency of payment dates. The payments (deposits) may be made weekly, monthly, quarterly, yearly, or at any other regular interval of time. Annuities may be calculated by mathematical functions known as "annuity functions". An annuity which provides for payments for the remainder of a person's lifetime is a life annuity. Types Annuities may be classified in several ways. Timing of payments Payments of an annuity-immediate are made at the end of payment periods, so that interest accrues between the issue of the annuity and the first payment. Payments of an annuity-due are made at the beginning of payment periods, so a payment is made immediately on issue. Contingency of payments Annuities that provide payments that will be paid over a period known...