Source : Free On-Line Dictionary of Computing

Ethernet address
     
         (Or "{MAC} address") The physical address
        identifying an individual {Ethernet controller} board.  An
        Ethernet addess is a 48-bit number aabbccddeeff where a-f are
        {hexadecimal} digits.  The first 24 bits, aabbcc, identify the
        manufacturer of the controller.  The Ethernet address is
        hard-wired on some controllers, stored in a {ROM} on some, and
        others allow it to be changed from software.  It is usually
        written as six hexadecimal numbers, e.g. 08:00:20:03:72:DC.
     
        See also {ARP}, {Internet address}.
     
        (1996-02-21)