In order to address my own mother, I would use the word "어머니."

In order to address someone else's mother, I would use the word "어머님." It comes down to honorific usage; please refer to the section Honorific nouns in the Wikipedia on Korean honorifics.

In order to address my own mother, I would use the word "어머니."

In order to address someone else's mother, I would use the word "어머님." It comes down to honorific usage; please refer to the section Honorific nouns in the Wikipedia entry on Korean honorifics.

In order to address my own mother, I would use the word "어머니."

In order to address someone else's mother, I would use the word "어머님." It comes down to honorific usage; please refer to this section on Wikipedia: https://en.wikipedia.org/wiki/Korean_honorifics#Honorific_nouns

In order to address my own mother, I would use the word "어머니."

In order to address someone else's mother, I would use the word "어머님." It comes down to honorific usage; please refer to the section Honorific nouns in the Wikipedia on Korean honorifics.