The Chinese word **阴险** is a compound adjective formed by combining two independent characters, each contributing distinct semantic layers. The first character, **阴** (yīn), originally meaning "shade" or "the moon," carries connotations of darkness, hiddenness, and negativity. The second character, **险** (xiǎn), means "dangerous," "risky," or "deceitful." When fused, the literal sense of "dark and dangerous" evolves metaphorically to describe a person’s character, specifically meaning **sinister, treacherous, or crafty**—someone who harbors malice and deceptive intentions beneath a concealed or outwardly normal appearance. Thus, the formation is a semantic synthesis where both components amplify each other to create an abstract quality of concealed malevolence.