sir
noun [ as form of address ] formal uk/sɜːr/ us/sɝː/ (also Sir)
B1 先生
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
Would you like to see the menu, sir? 您要看看菜单吗，先生?
"Did you hear what I said?" "Yes, Sir." “听到我说的话了吗？”“是的，先生。”
Compare: madam (WOMAN)MissMs
mainly UK（孩子对男性教师的称呼）老师
sometimes used by children to address or refer to teachers who are men
Can I go to the toilet, sir? 我可以上厕所吗，老师？
Indian English（用于男性、特别是权威人士的名字之后，用以表示礼貌或尊敬）先生
used after the name of a man, especially one who is in a position of authority, in order to be polite or show respect
John Sir 约翰先生
Dear SirB2 尊敬的先生（用于正式信函中称呼不知姓名的男性收信人；Dear sirs，即尊敬的各位先生，为正式商务信函的旧式信首称呼语）
used to begin a formal letter to a man whose name you do not know. "Dear Sirs" is an old fashioned way of beginning a letter to a company.
Dear Sir or Madam 尊敬的先生或女士，敬启者（用于正式信函中称呼不知性别的收信人）
used to begin a formal letter when you do not know if the person you are writing to is a man or a woman
- More examples
- Come hither, young sir!
- I'm sorry, sir, the salmon is off.
- Officer Clarke will show you where to go, sir.
- The seat of those trousers looks rather tight, sir - Would you like to try a larger size?
- Would you like to settle up now, sir?
Idiom
no siridiom US informal 决不，绝不，绝对不
certainly not
I'm not going to ride the subway, no sir! 我不会去乘地铁，绝对不会！