The process of verifying the identity of a user, process, or device, usually as a prerequisite for granting access to resources in an IT system.
SOURCE: SP 800-47
The process of discovering the true identity (i.e., origin, initial history) of a person or item from the entire collection of similar persons or items.
SOURCE: FIPS 201
An act or process that presents an identifier to a system so that the system can recognize a system entity (e.g., user, process, or device) and distinguish that entity from all others.