Picture one person being handed a sealed task by the people at the top, and then being sent somewhere to carry it. They are not a clerk following orders one at a time — the rank in high means they can decide, and when they speak, the body that sent them is speaking. What changes from use to use is only what is in the envelope: a problem, a country, or a piece of land.
Two branches
帶著一項任務被派出去的高階官員
這一支最貼近核心畫面：信封裡裝的是一個要處理的議題，人被派出去就是為了那件事。
noun · C1
A senior official, often a diplomat, who is formally put in charge of one particular area of work for a government or an international organisation — for example the United Nations High Commissioner for Refugees.
高級專員
大英國協之間的大使
信封裡裝的換成「一個國家」：被派出去的任務不是解決某個議題，而是長期代表自己的國家待在另一個國家。
noun · C1
In the Commonwealth, the official that one member country sends to another to do the job an ambassador does between other countries.
（大英國協）高級專員