The process of verifying the identity or other attributes claimed by or assumed of an entity (user, process, or device), or to verify the source and integrity of data. NIST SP 800-53: Verifying the identity of a user, process, or device, often as a prerequisite to allowing access to resources in an information system.

 Source: DRI

Authentication is the process of verifying the identity of a user or process in order to grant access to a system, service, or resource.