In what situation is the word 'sir' used?
"Sir" is a polite and formal way to address a man. It can be used in any situation where you want to address a man with respect, especially if they are older than you. The only time it is not used is when you should use another term for respect instead of "sir" like "professor" or "doctor". You can also use the term "Mister", abbreviated to "Mr.", however, this usually is said only together with a man's surname. If you don't know a man's surname and you want to address him with respect, you can just say "Sir". Ex: Here's your receipt, Sir. Ex: Thank you for your time, Mr. Smith.