The Chinese word "十五" is formed through the direct combination of two numeric characters: "十", which represents the value ten, and "五", which represents the value five. In this construct, "五" is appended to "十" in a sequential manner where "十" establishes the base decade, and "五" specifies the additional units, thereby creating the compound meaning of fifteen through simple addition within the character sequence. This formation reflects a common logical structure in Chinese numerals where the components are juxtaposed to convey a sum, resulting in a clear and efficient representation of the number.