sir

1. N-VOC People sometimes say sir as a polite way of addressing a man whose name they do not know, or an older man. For example, a shop assistant might address a male customer as sir. 先生 (對男性的客氣稱呼)[禮貌]

Excuse me sir, but would you mind telling me what sort of car that is?

對不起，先生，您能告訴我那是什麼樣的汽車嗎？

2. N-TITLE Sir is the title used in front of the name of a knight or baronet. (爵士或從男爵名字前的頭啣) 爵士

She introduced me to Sir Tobias and Lady Clarke. 她把我介紹給托拜厄斯爵士和尅拉尅夫人。

3. CONVENTION You use the expression Dear Sir at the beginning of a formal letter or a business letter when you are writing to a man. 敬啓者 (常用於正式函件或商務(wù)函件)

Dear Sir, Enclosed is a copy of my résumé for your consideration. 敬啓者，玆附上我的簡歷一份，請予以考慮。