(~s)
Frequency: The word is one of the 1500 most common words in English.
1.
People sometimes say ~ as a very formal and polite way of addressing a man whose name they do not know or a man of superior rank. For example, a shop assistant might address a male customer as ~.
Excuse me ~, but would you mind telling me what sort of car that is?...
Good afternoon to you, ~.
N-VOC politeness
2.
Sir is the title used in front of the name of a knight or baronet.
She introduced me to Sir Tobias and Lady Clarke.
N-TITLE
3.
You use the expression Dear ~ at the beginning of a formal letter or a business letter when you are writing to a man. You use Dear ~s when you are writing to an organization.
Dear Sir, Your letter of the 9th October has been referred to us.
CONVENTION