How to Address a ‘Sir’ (Knight)
‘Sir’ is not a rank or office. But it is an honorific used in oral and written address of a British knight: Sir Paul (Paul McCartney), Sir Elton (Elton John).
Follow the link to Knight for the forms of address and use of Sir. How to use Maam
How to Use Sir and Ma’am
Oral use of Sir and Ma’am elevates the formality of the conversation.
In hierarchical organizations/environments Sir and Ma’am are signs of respect. For example, in the Armed Services it’s standard to address anyone of higher in rank (e.g. officers by enlisted personnel) by (Rank)+(Name) first, then as Sir/Ma’am thereafter.
In formal households children might be taught to address their elders as Sir or Ma’am. Thus, to many it is appropriate to use these when addressing someone older.
I take a spin class every Saturday — the instructor always calls me Sir … Because (I think it is his reasoning) he has noticed that I am by far the oldest person in class. I think it’s funny, but I bet not everyone would.
If someone reacts negatively to being addressed as Sir or Ma’am, they are probably very egalitarian and don’t like what they see as your implication of a lower/higher relationship. Or they think you are suggesting they are old. In either case, try Good Morning rather than Good Morning, Sir or Good Morning Ma’am..
– Robert Hickey How to use Maam