The word **遗书 (yíshū)** is a compound noun formed by combining the character **遗 (yí)**, meaning "to leave behind" or "bequeath," with the character **书 (shū)**, meaning "document" or "writing." In this construction, **遗** acts as a modifier describing the nature of the **书**, so the term literally translates to "a writing left behind." It specifically refers to a document left by someone before their death, commonly understood as a **last will and testament** or, in a more tragic context, a **suicide note.** The formation follows the common Chinese syntactic pattern where the first character modifies the second, precisely defining the type of "writing" as one that is posthumous or final.