1. A marking applied to information, indicating the estimated damage to the national interest that would be caused by its unauthorized disclosure, and used to determine the minimum standards of protection that should be applied. 2. A component of a security clearance and/or security class used for computing access rights and controlling information flow. Note: Access rights are granted when the classification element of the security clearance is greater than or equal to that of the security class. See also: Category, Caveat, and Dominance.