1. In a network, such as a communications network or a computer network, a device that performs the interface functions, such as code conversion, protocol conversion, and buffering, required for communications into and out of the network. 2. A device primarily used within a local area network (LAN) to allow a number of independent devices, with varying protocols, to communicate with each other. Common abbreviationNID.Note 1: The network interface device (NID) converts each device protocol into a common transmission protocol. Note 2: The transmission protocol may be chosen so as to directly accommodate a number of the devices used within the network without the need for protocol conversion for those devices by the network interface device (NID). 3. A device used to access a bus or a network. Note: An example of a network interface device (NID) is a modem. Synonyms bus interface unit,  network interface unit. See also access,  buffer,  bus,  code,  code conversion,  communicate,  communications adapter,  communications network,  computer network,  convert,  device,  interface,  local area network,  medium interface point,  modem,  network,  protocol,  transmission control protocol,  Transmission Control Protocol.