결혼식이 · 결혼식을
wedding, wedding ceremony
Example
다음 달에 언니의 결혼식이 있어요.
My older sister's wedding is next month.
Word parts
결 tie, bind+혼 marriage+식 ceremony
-식 = ceremony: 결혼식, 졸업식, 입학식.
Good to know
Guests usually give cash in an envelope (축의금) instead of buying a registry gift.