Protocol is a system of rules about the correct way to act in formal situations.
He has become something of a stickler for the finer observances of royal ~.
...minor breaches of ~.
A ~ is a set of rules for exchanging information between computers. (COMPUTING)
A ~ is a written record of a treaty or agreement that has been made by two or more countries. (FORMAL)
...the Montreal Protocol to phase out use and production of CFCs...
A ~ is a plan for a course of medical treatment, or a plan for a scientific experiment. (AM FORMAL)
...the detoxification ~.