Short-Forms. 

Everyone knows 'Seongsaenim" means Teacher right? 

But what IS the short-form of 'Teacher?" 

Well, you can use it. It is NOT disrespectful if you use short-forms.  

In English, the english short-form for "teacher" is "cher" right? (when you say teacher very fast, it will end up as "Cher") 

In Korea, its called 'Saem". ("Cher" in english)   "샘" <--- this is how you write it. 

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Formal.

When you have a close-relationship with a guy/girl that is 2 years/1 year older than you, you will call him/her "Hyung/Oppa/Noona/Unnie"
HOWEVER, if you have someone who is elder than you by more than 1 GENERATION, you must call him "hyung-nim" That only applys to the boys. 

Hyung= A younger boy calling a boy who is older than him. '형' Its pronounced as hyeong. 
Oppa= A younger girl calling a boy who is older than her. ' 오빠' Its pronounced as oppa.
Noona= A younger boy calling a girl who is older than him. ' 누나' Its pronounced as nuna.
Unnie= A younger girl calling a girl who is older than her.  ' 언니' Its pronounced as eonni.

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If you have a younger sibling, you can say "yeodongsaeng" or "namdongsaeng"  

"Yeodongsaeng" means "Younger Sister."
"Namdongsaeng" means "Younger Brother" 

Yeodongsaeng = 여동생
Namdongsaeng = 남동생
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