The word "海陆空" is formed by directly combining three individual characters: 海 (hǎi), meaning "sea"; 陆 (lù), meaning "land"; and 空 (kōng), meaning "air". Each character represents a distinct domain, and when sequenced together, they create a single compound term that collectively refers to the maritime, terrestrial, and aerial spheres, typically in contexts such as military branches or transportation systems.