sir

音标发音

sir的基本意思是“先生”,是对男士的一种尊称,多用于长者、上级或服务业中对男顾客的称呼。是可数名词,常用于单数形式。sir不可同姓氏连用,但可用于名字之前或名字与姓之前。
sir通常用于正式书信的开头,如Dear Sir或Sirs,首字母要大写。
sir的另一意思是“爵士”。在英国的非正式口语中, sir还可作“某人的男教师”解。
在口语中,Yes, sir或No, sir可用于回答女性的提问。
与sir相对应的阴性名词是madam。

used as a formal and polite way of speaking to a man, especially one who you are providing a service to or who is in a position of authority

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.
Sir is the title used in front of the name of a knight or baronet.
You use the expression Dear Sir at the beginning of a formal letter or a business letter when you are writing to a man.