무 (Nothing) refers to the absence of anything or the state of non-existence. In philosophy, it often raises questions about the nature of reality and existence. The concept challenges our understanding of what it means to "have" or "be," prompting discussions in various fields, including metaphysics and existentialism. In everyday language, 무 can describe a lack of substance or value, such as in the phrase "무의미" (meaningless). It can also be used in contexts like Zen Buddhism, where the idea of emptiness is central to understanding the nature of the self and the universe.