The word "危在旦夕" is formed by combining four characters: "危" meaning danger, "在" meaning to be at or in, and "旦夕" which together represent a very short timeframe, from morning ("旦") to evening ("夕"). Literally, it translates to "danger is at dawn and dusk", but idiomatically it conveys that peril is imminent within a brief period, emphasizing immediate threat through this temporal metaphor.