The Chinese word 直线 (zhíxiàn), meaning "straight line", is a modifier-head compound formed through semantic combination. The first character 直 (zhí) means "straight" or "direct", functioning as a descriptive modifier. The second character 线 (xiàn) means "line" or "thread", serving as the core noun, or "head", of the word. Therefore, the compound literally and logically describes a "straight line", where the modifier 直 specifies the particular quality of the head noun 线. This transparent and intuitive structure is common in Chinese for creating precise technical and everyday vocabulary.