20 C.F.R. § 219.2
As used in this subpart-
Annuity means a recurring payment due an entitled person for a calendar month and made to him or her on the first day of the following month.
Apply means to sign a form or statement that the Board accepts as an application.
Claimant means the person who files an application for an annuity or lump-sum payment for himself, herself, or some other person.
Benefit means any employee annuity, spouse annuity, survivor annuity, or lump-sum payment under the Railroad Retirement Act.
Convincing evidence means one or more pieces of evidence that proves to the satisfaction of the Board that an individual meets a requirement for eligibility for benefits. See § 219.7 for guides the Board uses in deciding whether evidence is convincing.
Eligible means that a person meets all of the requirements for payment of benefits but has not yet applied therefor.
Entitled means that a person has applied for and has proved his or her right to payment of benefits.
Evidence means any record or document or testimony that helps to show whether a person is eligible for benefits. It may also be used to establish whether the person is still entitled to benefits.
Representative means a person who acts on behalf of a claimant in regard to his or her claim for benefits from the Board and in the presentation of evidence to support the claim.
20 C.F.R. §219.2