I thought 씨's function was to identify a name in a sentence. Is that the case? In which cases would I use 씨? Would I address my friend as ___씨? Or can they just be called by their name?
There are usually three ways to identify a name: adding 님, adding 씨, and just using the name. For example, if you call a close friend named 영수 Young-soo:
- 영수야 sounds good. (Similar to Hey Young-soo!)
- 영수씨 sounds weird. (Similar to Hello Mr Yong-soo!)
- 영수님 sounds awkward. (Similar to Hello Mr Yong-soo!)
But, if you have a manager 영수 in your company:
- 영수야 sounds bad!
- 영수씨 is bad!
- 영수님 is not bad in some companies. (Usually, family name + position + 님 is used. 김 선임님...)
Also, if you meet a mutual friend 영수 at first time:
- 영수야 is not good. (Because it's first time!)
- 영수씨 is good.
- 영수님 is up to the situation.
In my experience, the term 씨 is used for people who you do not know well, but who are roughly in your peer group or sometimes lower. It is used when you desire to be respectful, but not TOO respectful. I have never personally heard it used on children, even though they tend to be considered lower in status. And if you use it on a peer whom you know well, it would also sound weird. It would be like calling your best friend "sir."
The setting where I hear 씨 used the most is probably at work. When I am talking about (or to) a colleague I do not know well and I am about their age and status at the company, I use 씨. This is only proper when the person has no real title. If they are a supervisor or a boss, do not use 씨.
Personally, I use the person's full name plus 씨 if I do not know them much at all (예: 박서원씨). If I know them a bit better, or they are a bit lower ranking, I use just the given name (no family name; 예: 동희씨). Since I am not Korean and am not always capable of fine nuances, I try to avoid using just family name + 씨 when referring to someone. This feels less formal and sometimes I almost feel rude saying it.