-(으)시-
RuleVerb/adjective stem + -(eu)si-: a pre-final ending that honors the subject. After a vowel stem use -si-; after a consonant stem use -eusi-.
Curiosity
If you have added kkeseo to the subject, can the verb stay unchanged? seonsaengnim-kkeseo gada feels somehow incomplete.
Intuition
The honor is completed on the verb. By inserting -si- between the stem and the ending, the verb itself bows: "the doer of this action is to be respected."
Visualization
Climb step by step from plain to honored to formal-polite: gada → gasida → gasimnida.
Honorificsubject honorification
가다gadaplain (dictionary)
Essence
-(eu)si- splits into -si-/-eusi- by batchim (gada→gasida, ikda→ileusida). Some verbs change shape entirely: meokda→deusida, jada→jumusida, itda→gyesida. The honorific gyesida ("to be/stay") is only for people, distinct from isseusida used for honored possession.
Examples
할머니께서 주무세요.
Grandmother is sleeping. (honorific)
사장님이 지금 안 계세요.
The boss is not here right now. (honorific)
아버지께서 책을 읽으십니다.
Father is reading a book. (honorific)
Mini-quiz
Add subject honorification to ilkda ("to read"). (consonant-final stem)