신데요

are

→ 이다
신 Honorific copula + 데 Background/contrastive connective + 요 Polite speech
auxiliary · formal Rare #29,744
are Honorific form of 이다, used after a noun. The ending -(으)ㄴ데요 often softens a question or invites a response.
KO: 지금 어디신데요?
EN: Where are you right now?
Conjugation of 이다
Admirative present
Subjunctive future
Subjunctive past
Potential
Jussive
Necessitative
Quotative future
Subjunctive imperfect
Irrealis past
Interrogative imperfect
Potential past
Interrogative present

아, 어디 신데요?

Oh, where are you?

— Miracle in Cell No. 7 (2013)

아이, 뭐 지금 뭐 어디 신데요?

Hey, where are you right now?

— Love Untangled (2025)

누구 신데요?

Who are you?

— 자전거 도둑 (1948)

아니, 선생님 무슨 문제 신데요?

No, teacher, what's the problem?

— 데드맨스 와이어 (2026)