term of address for a man
"When the waiter arrived at our table, I politely asked him to bring us some more water by saying, "Sir, could you help us?""
a title used before the name of knight or baronet
"Sir Arthur Conan Doyle was famous for writing many Sherlock Holmes stories."
A man of a higher rank or position.
"The signboard alternated between displaying SIR and Sir to accommodate different styles."
Initialism of surface insulation resistance.
Alternative letter-case form of sir.
In plain English: Sir is a polite way to address an older man, especially someone you respect or are talking to formally.
"The young boy called out to the man in the suit, respectfully asking if he could be his sir."
To address (someone) using "sir".
"The young man bowed slightly and addressed his commanding officer as sir before receiving the new orders."
In plain English: To sir means to serve someone, usually by giving them food or drinks.
"He tried to sir the angry customer by offering him a free meal, but the man just walked away."
Usage: Use this verb form only when describing an action where someone explicitly addresses another person as "sir," such as in military drills or formal ceremonies. It is distinct from the noun used to show respect, so avoid confusing it with phrases like "he sirred me" unless a direct command was given using those exact words.
Initialism of susceptible-infected/infectious-removed/recovered.
"In my epidemiology class, I quickly learned that SIR stands for susceptible-infected-infectious-recovered and is a common model used to track disease spread."
"The sir suit looked very formal at the wedding."
The word "sir" comes from the Old French term for "master" or "lord," which was borrowed from Latin words meaning "older" or "old." It originally referred to an elder person before evolving into a title of respect.