You use expressions such as Your Excellency or His Excellency when you are addressing or referring to officials of very high rank, for example ambassadors or governors.
例句
I am reluctant to trust anyone totally, Your Excellency...我不想完全相信任何人，閣下。His excellency the President will be waiting for you in the hall.總統閣下會在大廳等你。
英漢詞典釋義
n.
(X-)閣下(對大使、大臣、總督、主教等的尊稱)
After you, your excellency.閣下，您先請。
英英詞典釋義
Noun
1. a title used to address dignitaries (such as ambassadors or governors); usually preceded by Your or His or Her;