The user name, or username, by which a person is identified to a computer system or network. A user commonly must enter both a user ID and a password as an authentication mechanism during the logon process. If the system or network is connected to the Internet, the username typically is the leftmost portion of the e-mail address, which is the portion preceding the @ sign. In the e-mail address email@example.com, for example, ray is the username. User ID is synonymous with username. See also password.