The word 性别 is formed by combining two characters, each contributing a core concept: 性 (xìng), which denotes inherent nature, essence, or character, and 别 (bié), which denotes distinction, differentiation, or category. Together, they conceptually fuse to mean "the category/distinction of innate nature", directly pointing to the classification of biological sex or socially constructed gender. The formation is not grammatical but ideographic, building the abstract idea through the logical juxtaposition of these two fundamental notions.