sir

Từ điển Oxford Advanced Learner 8th

sir [sir sirs] BrE [sɜː(r)] NAmE [sɜːr] BrE [sə(r)] NAmE [sər] noun
1. used as a polite way of addressing a man whose name you do not know, for example in a shop/store or restaurant, or to show respect
• Good morning, sir. Can I help you?
• Are you ready to order, sir?
•‘Report to me tomorrow, corporal!’ ‘Yes, sir!’
•‘Thank you very much.’ ‘You're welcome, sir. Have a nice day.’
compare ↑ma'am
see also ↑madam
2. Dear Sir/Sirsused at the beginning of a formal business letter when you do not know the name of the man or people that you are dealing with
•Dear Sir/Sirs
•Dear Sir or Madam
3. Sira title that is used before the first name of a man who has received one of the highest British honours (= a ↑knight ), or before the first name of a ↑baronet
•Sir Paul McCartney
• Thank you, Sir Paul.
compare Lady
4. (BrE)used as a form of address by children in school to a male teacher
• Please, sir, can I open a window?
compare ↑miss
Idioms: ↑no sir! ▪ ↑no siree! ▪ ↑yes sir! ▪ ↑yes siree!

Word Origin:
Middle English: reduced form of ↑sire.