[1] The word is also used informally for people who are known, without national appointment, to represent certain professions, activities, and fields of endeavor, such as sales.
Countries may choose to maintain diplomatic relations at a lower level by appointing a chargé d'affaires in place of an ambassador.
The term is derived from Middle English ambassadour, Anglo-French ambassateur; akin to Old High German ambaht, "service".
In some cases, the foreign government might reverse its approval by declaring the diplomat a persona non grata, i.e. an unacceptable person.
When two nations are conducting a trade, it is usually advantageous to both parties to have an ambassador and perhaps a small staff living in the other land, where they act as an intermediary between cooperative businesses.
The use and creation of ambassadors during the 15th century in Italy has had long-term effects on Europe and, in turn, the world's diplomatic and political progression.
Ambassadors now normally live overseas or within the country to which it is assigned for long periods of time so that they are acquainted with the culture and local people.
Ambassadors hold the highest diplomatic rank and have precedence over chargés d'affaires, who are accredited by the foreign minister.
The difference in accreditation is also reflected in the formal titles of envoys to foreign and Commonwealth states: e.g., British High Commissioners are formally titled "The High Commissioner for His Majesty's Government in the United Kingdom", whereas British Ambassadors to foreign countries are known as "His Britannic Majesty's Ambassador".
Historically, presidents or prime ministers have commissioned special diplomatic envoys for specific assignments, primarily overseas but sometimes also within the country as ambassadors-at-large.
While the title generally reflects the ambassador's second head position as head of a diplomatic mission, in some countries the term may also represent a rank held by career diplomats, as a matter of internal promotion, regardless of the posting, and in many national careers it is quite common for them to be appointed to other functions, especially within the ministry/ministries in charge of foreign affairs, in some countries in systematic alternation with actual postings.
In a less formal sense, the phrase is used for high-profile non-diplomatic representatives of various entities (rarely states), mainly cultural and charitable organizations, often as willing figureheads to attract media attention; for example, film and pop stars make appeals to the public at large for United Nations activities, sometimes during press-swarmed visits in the foreign country.
[10] Japan adopted the cartoon character Hello Kitty as their official goodwill and tourism ambassador to China and Hong Kong in 2008.
[11] According to Brain, the job of a brand ambassador was undertaken typically by a celebrity or someone of a well-known presence, who was often voluntary or paid considerably for their time and effort.
[12] In French-speaking regions such as metropolitan France, Guadeloupe, Réunion, Quebec, or Wallonia, the title of ambassadeur personne is used.
Holders of this rank may not necessarily possess diplomatic authority or accreditation to any state, though nearly all have previously served as an Ambassador Extraordinary and Plenipotentiary during their careers.