The word 擅自 (shànzì) is a compound formed by combining two characters: 擅 (shàn), which carries the meaning of "to monopolize" or "to act without authorization", and 自 (zì), meaning "self" or "oneself". Together, they create an adverb that literally conveys the idea of "acting on one's own authority", but its actual usage almost always implies a negative judgment, meaning to act presumptuously, without permission, or beyond one's proper authority. The formation follows a common pattern in Chinese where an action (擅) is modified by an agent (自) to specify that the action is undertaken by the self in an unauthorized or inappropriate manner, resulting in a term that describes a willful overstepping of boundaries.