The word "骡马" is formed by combining two characters: "骡", meaning mule, and "马", meaning horse. Each character represents a distinct animal, and when joined, they create a compound noun that collectively refers to both mules and horses, typically used in contexts like livestock or transportation. The character "骡" itself includes the "马" radical, indicating its relation to horse-like animals, but in this compound, the two characters function as independent semantic units to denote a broader category.