A means of restricting access to system resources based on the sensitivity (as represented by a label) of the information contained in the system resource and the formal authorization (i.e., clearance) of users to access information of such sensitivity.
Sources:
NIST SP 800-44 Version 2 under Mandatory Access Control

  A hardware address that uniquely identifies each component of an IEEE 802-based network. On networks that do not conform to the IEEE 802 standards but do conform to the OSI Reference Model, the node address is called the Data Link Control (DLC) address.
Sources:
NIST SP 800-18 Rev. 1 under Media Access Control Address

  A family of secret-key cryptographic algorithms acting on input data of arbitrary length to produce an output value of a specified length (called the MAC of the input data). The MAC can be employed to provide an authentication of the origin of data and/or data-integrity protection. In this Recommendation, approved MAC algorithms are used to determine families of pseudorandom functions (indexed by the choice of key) that are employed during key derivation.
Sources:
NIST SP 800-108r1 [August 2022 (Includes updates as of 02-02-2024)] under message authentication code

  A cryptographic checksum on data that uses a symmetric key to detect both accidental and intentional modifications of the data.
Sources:
NISTIR 7711 under Message Authentication Code