The Chinese word **下颚 (xià'è)**, meaning "lower jaw" or "mandible," is formed through a straightforward **modifier-head compound** structure common in Chinese morphology. The first character **下 (xià)** acts as a descriptive modifier meaning "below" or "lower," which specifies the location of the noun denoted by the second character **颚 (è)**, which is the core meaning "jaw" or "palate." Therefore, the compound logically and transparently combines to mean "the jaw that is below," precisely distinguishing it from the upper jaw (上颚). This formation is analogous to English compound words like "downstairs," where spatial direction modifies a primary noun.