The Chinese word 悔恨 (huǐhèn), meaning "deep regret" or "remorse," is a compound formed by combining two synonymous or closely related characters: 悔 (huǐ), which means "to regret" or "repent," and 恨 (hèn), which means "to resent" or "feel bitter remorse." This structure, known as a coordinative or synonymous compound, is common in Chinese word formation, where two morphemes with similar meanings are joined to create a single, often more emphatic or nuanced concept. In this case, the combination intensifies the emotional weight, conveying a profound sense of sorrow and self-reproach that blends the ideas of regret (悔) and lingering resentment or anguish (恨) over a past action.