The name for letters given to an ambassador by their chief of state, and addressed to the chief of state of the host country. Credentials are delivered to the chief of state by the ambassador in a formal credentials ceremony, which generally takes place shortly after the ambassador’s arrival at a new post. Until this ceremony has taken place, the ambassador is not formally recognized by the host country and cannot officially act as an ambassador. The letters are termed “letters of credence” because they request the receiving chief of state to give “full credence” to what the ambassador will say on behalf of their government.