20 CFR 216.1: Introduction.

This part explains when an individual is eligible for a monthly annuity under the Railroad Retirement Act. An individual eligible for an annuity as described in this part may become entitled to an annuity only in such amount as set forth in parts 225 through 229 of this chapter

(a) Regular annuity. A regular monthly annuity is provided for:

(1) An employee who retires because of age or disability;

(2) An employee's spouse or divorced spouse; or

(3) The widow, widower, child, parent, remarried widow or widower, or surviving divorced spouse of an employee.

(b) Supplemental annuity. An employee who retires because of age or disability may also be entitled to a supplemental annuity.