20 C.F.R. § 404.602
For the purpose of this subpart-
Applicant means the person who files an application for benefits for himself or herself or for someone else. A person who files for himself or herself is both the applicant and the claimant.
Application refers only to an application on a form described in § 404.611 .
Benefits means any old-age, disability, dependents', and survivors' insurance benefits described in subpart D, including a period of disability.
Claimant means the person who files an application for benefits for himself or herself or the person for whom an application is filed.
We, us, or our means the Social Security Administration (SSA).
You or your means, as appropriate, the person who applies for benefits, the person for whom an application is filed, or the person who may consider applying for benefits.
20 C.F.R. §404.602