Korean Family Titles
처제
cheoje · Wife's younger sister
Relationship
my wife → her younger sister
Who uses it
A husband, about his wife's younger sister.
When you call them
Call her 처제.
When you talk about them
To others, 처제.
Example
처제, 취업 축하해!Cheoje, congrats on the new job!
Based on the standard etiquette of the National Institute of Korean Language; families and regions vary.