The word "室内" (shìnèi) is formed through a logical semantic combination of two individual characters: "室" (shì), meaning "room" or "enclosed space", and "内" (nèi), meaning "inside" or "interior". When combined, they create a compound word that literally translates to "the inside of a room" or "within a space", which functionally means "indoor" or "interior" as an adjective (e.g., indoor activities) or a noun (e.g., the interior of a building). This formation follows a common Chinese word-construction pattern where two related morphemes are placed together to specify a precise, spatial concept, with the first character ("室") defining the domain and the second ("内") describing the relative position within it.