act of confirming the truth of an attribute of a datum or entity, often used as part of access control

Authentication (pronounced /ɔˈθɛntɪˌkeɪt/ "aw-then-ti-keyt") (from Greek αυθεντικός; real or genuine, from authentes; author) is the actions taken to establish or verify something (or someone) as authentic. It is the method of verifying claims made by someone about the thing. This might involve confirming the identity of a person, the origins of an object (or something), or to make sure that a computer program (or user) is a trusted one. People are usually authenticated by something they know (password), something they have (key), or something they are (biometrics).