/ sɜː(r); NAmE ; sə(r)/ 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 / Sirs used 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.
Sir a 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 .