Korean Family Titles
외할머니
oehalmeoni · Grandmother (mother's mother)
Relationship
my mother → her mother
Who uses it
About your mother's mother.
When you call them
Face to face, 할머니. Kids sometimes say 외할머니 to tell two grandmas apart, or use where she lives, like 부산 할머니.
When you talk about them
To others, 외할머니 — or just 할머니.
Example
방학마다 외할머니 댁에 가요.I go to my grandma's every school break.
Based on the standard etiquette of the National Institute of Korean Language; families and regions vary.