「懸案」指的是無法解決而擱置的案件或問題，也可以泛指歷史遺留的未解決事項。
懸案是一個涵蓋廣泛的概念，指任何長期未能解決的案件或問題，通常帶有無法突破、懸而未決的意味。

"Cold cases" refer to cases or problems that cannot be resolved and have been shelved. They can also refer to unresolved matters left over from history.
Cold cases are a broad concept, referring to any cases or problems that have not been resolved for a long time, usually implying that they are unbreakable and unresolved.