A pension is a fund into which a sum of money is added during an employee's employment years, and from which payments are drawn to support the person's retirement from work in the form of periodic payments. A pension may be a "defined benefit plan" where a fixed sum is paid regularly to a person, or a "defined contribution plan" under which a fixed sum is invested and then becomes available at retirement age. Pensions should not be confused with severance pay; the former is usually paid in regular installments for life after retirement, while the latter is typically paid as a fixed amount after involuntary termination of employment prior to retirement.