The Chinese word **油脂 (yóuzhī)**, meaning "oil and fat," is a **compound word formed by combining two semantically related characters**. It follows a common pattern in Chinese morphology where two independent, synonymous, or closely associated characters are joined to create a single, more precise or general term. Here, **油 (yóu)** primarily means "oil" (often liquid at room temperature, like plant oil), and **脂 (zhī)** means "grease" or "fat" (often solid, like animal fat). By combining them, the word **油脂** broadly encompasses all forms of fats and oils, capturing the full spectrum of the substance in both its liquid and solid states, thus enhancing semantic clarity and scope through conjunction.