The word 空虚 is formed by combining two characters, 空 and 虚, which both independently carry connotations of emptiness. 空 primarily suggests a physical or spatial void, like an empty room or sky, while 虚 implies a more abstract, insubstantial hollowness, like weakness or a lack of solid foundation. When paired, they create a powerful, layered metaphor where the tangible emptiness of 空 merges with the intangible, psychological hollowness of 虚 to express a profound state of existential or emotional void, a feeling that something is missing not just in one's surroundings, but within one's spirit or life.