A letter of credence is a formal letter usually sent by one head of state to another that formally grants diplomatic accreditation to a named individual (usually but not always a diplomat) to be their ambassador in the country of the head of state receiving the letter. A letter of recall is the opposite, a letter sent from one head of state to another head of state recalling an ambassador, either as a means of diplomatic protest (see letter of protest) or because the diplomat is being reassigned elsewhere and is being replaced by another envoy.