(1) An original copy or record of a document. (2) A code of diplomatic or military rules of behavior.
Example:
The guests at the governor's dinner were introduced and seated according to the strict protocol governing such occasions.
Protocol comes from a Greek word that refers to the first sheet of a papyrus roll. As an English word, protocol originally meant "a first draft or record," after which it came to mean specifically the first draft of a diplomatic document, such as a treaty. The "diplomatic" connection led eventually to its current meaning of "rules of behavior." Someone wearing Bermuda shorts and sandals to a State dinner at the White House would not be acting "according to protocol." Protocol is also now used to refer other kinds of rules, such as those for doing a scientific experiment or for handling computer data.