The Chinese word **室外** is formed as a compound word by combining two independent characters: **室** (shì), meaning "room" or "indoor space," and **外** (wài), meaning "outside" or "exterior." When placed together, they create a new concept through a straightforward modifier-head structure, where **外** ("outside") acts as the core meaning, modified by **室** ("room") to specify the type of "outside" being referred to—literally "the outside of a room" or "outdoors." This logical, semantic combination is a common method in Chinese word formation, producing a term whose meaning is directly derived from the sum of its parts.