godan verb (-ru), intransitive verb
take over for; stand in for; substitute for
Used when a person temporarily or permanently takes over another person's role, duty, or position. Often implies acting on behalf of someone else.
急に社長が倒れたので、副社長が成り代わって会議を進めた。
Since the president suddenly collapsed, the vice president took over and proceeded with the meeting.
母が病気のときは、私が成り代わって家事をした。
When my mother was sick, I stood in for her and did the housework.
godan verb (-ru), intransitive verb
Used when one thing or person replaces another, often implying a change in state or function. Can be used for objects, roles, or abstract concepts.
古い制度に成り代わって、新しいルールが導入された。
New rules were introduced, replacing the old system.
紙の辞書に成り代わって、電子辞書が主流になった。
Electronic dictionaries have taken the place of paper dictionaries and become mainstream.