The compound word **悬案 (xuán'àn)** is formed through the morphological process of **modification (偏正结构)**, where the first character **悬 (xuán)**, meaning "to hang" or "to suspend," figuratively modifies the second character **案 (àn)**, meaning "case" or "legal matter." Together, they create a metaphorical meaning: a case that is metaphorically "left hanging" or suspended in an unresolved state, thus directly translating to and signifying an **"unsolved case"** or a **"pending case"** that remains open due to lack of evidence or a conclusive verdict.