hardware address - (sometimes called MAC address or ethernet address) All ethernet cards, whether wired or wireless, have a 12-digit hexidecimal number (which means it can contain the letters A through F in addition to numerals) that uniquely identifies it. When you connect your machine to the network, the network uses this number to verify that your machine is registered. For information on how to find your card's hardware address, see Finding Your Hardware Address. An example of a hardware address is 00E02938A48C.