Someone who has been given full power to act and decide, especially a government's representative in another country. In diplomacy it is a title as much as a job: an ambassador extraordinary and plenipotentiary may sign a treaty without running home for every yes.

Someone who has been given full power to act and decide指被授予完整權力去行動、做決定的人, especially a government's representative in another country尤其是一個政府派駐到另一個國家的代表。In diplomacy it is a title as much as a job在外交上，這既是一個頭銜，也是一份工作: an ambassador extraordinary and plenipotentiary may sign a treaty一位ambassador extraordinary and plenipotentiary（特命全權大使）可以簽訂條約 without running home for every yes不用每件事都跑回國內請示同意。

The word also works as an adjective: plenipotentiary powers, a plenipotentiary envoy. It is heavy, formal English — you meet it in treaties and history books, not in everyday talk.

The word also works as an adjective這個字也可以當形容詞用: plenipotentiary powers, a plenipotentiary envoyplenipotentiary powers（全權）、a plenipotentiary envoy（全權特使）。It is heavy, formal English這是很正式、厚重的英文——you meet it in treaties and history books你會在條約和歷史書裡遇到它, not in everyday talk而不是日常對話裡。

Though actually it does not mean 'a very powerful person' in general; the power is borrowed and bounded: full for that mission, because the government handed it over.

Though actually it does not mean 'a very powerful person' in general不過實際上，它並不是泛指「一個非常有權力的人」; the power is borrowed and bounded這份權力是被借來的，而且有範圍限制: full for that mission只在那項任務上是完整的, because the government handed it over因為是政府把權力交給了他。