사인은

as for the cause of death; the cause of death is

→ 사인

phrase Rare #15,621

as for the cause of death; the cause of death is 사인 means “cause of death” in this context, and 는 is the topic marker. Do not confuse 사인 with 사인 meaning “signature” or “autograph.”

KO: 사인은 심장마비로 보고서에 쓰겠습니다.

EN: I’ll write the cause of death as a heart attack in the report.

사인은 뭐 야, 코코?

What's the sign, Coco?

— 블레이드 러너 2049 (2017)

소령님, 사인은 뭘로 보고서 에 쓸 사인 심장마비 라고 해

Major, what should I put as the cause of death in the report? Say cardiac arrest.

— 무방비 도시 (1945)

사인은 뭐래?

What did they say the cause of death was?

— 브로커 (2022)