n.
    - the official procedure or system of rules governing affairs of state or diplomatic occasions. ▸the accepted code of procedure or behaviour in a particular situation. 
- the original draft of a diplomatic document, especially of the terms of a treaty agreed to in conference and signed by the parties. ▸an amendment to a treaty or convention. 
- a formal record of scientific experimental observations. ▸a procedure for carrying out a scientific experiment or a course of medical treatment. 
- Computing  a set of rules governing the exchange or transmission of data between devices.
Etymology
  ME (denoting the original note of an agreement): from OFr. prothocole, via med. L. from Gk prōtokollon ‘first page, flyleaf’.