Definitions

A minimum equipment list (MEL) is a list which provides for the operation of aircraft, subject to specified conditions, with particular equipment inoperative (which is) prepared by an operator in conformity with, or more restrictive than, the MMEL established for the aircraft type.

The master minimum equipment list (MMEL) is a list established for a particular aircraft type by the organisation responsible for the type design with the approval of the State of Design which identifies items which individually may be unserviceable at the commencement of a flight. The MMEL may be associated with special operating conditions, limitations or procedures.

Source: ICAO Annex 6: Operation of Aircraft