how do I use "sir"

"Thank you, sir / ma'am." is a bit more respectful and acknowledging than a simple "thank you."

In Canada, here's how the word 'sir' is used. As you can see, it's not very cmmon.,

We start a formal letter with 'Dear Sir', if we do not know the person's name.

In stores, sales staff sometimes address male customers as 'sir', eg May I help you, sir?

AnonymousWhen is the word "sir" used so that I am not too polite too formal

If you want to remain informal, don't use "sir" at all. In the past 10 years I have only heard it once or twice (California). Here it is considered as a term used almost exclusively in the military services (and somewhat in high-end hotels). I am addressed as "sir" from one woman a

In the past, some posters here have addressed me as "Sir," but my moderator friends set them straight fairly quickly.