The word **下滑 (xiàhuá)** is formed through the morphological process of **compounding**, combining two independent characters: **下 (xià)**, meaning "down" or "descend," and **滑 (huá)**, meaning "slide" or "slippery." Together, they create a **verb + result/direction complement** structure where 下 acts as a directional complement indicating the downward trajectory of the action denoted by 滑 ("to slide"). This results in a new, specific meaning—"to slide down," "to decline," or "to drop"—which is a metaphorical extension from the literal physical action to describe abstract downturns in areas like economics, performance, or quality.