Ambassadors are diplomats of the highest rank, formally representing the head of state, with plenipotentiary powers (i.e. full authority to represent the government). In modern usage, most ambassadors on foreign postings as head of mission carry the full title of Ambassador Extraordinary and Plenipotentiary. "Ordinary" ambassadors and non-plenipotentiary status are rarely used, although they may be encountered in certain circumstances. The only difference between an extraordinary ambassador and an ordinary ambassador is that while the former's mission is permanent, the latter serves only for a specific purpose