室内

室内 means 'indoor' or 'inside.' It refers to a space enclosed by walls, such as a room or building, and is often used to describe activities, conditions, or environments that take place inside rather than outside.

The character 室 (shì) means 'room' or 'building,' while 内 (nèi) means 'inside' or 'within.' Together, they form the concept of being inside a structure or enclosed area.

室内 is commonly used in contexts like indoor sports, indoor plants, or indoor lighting. It contrasts with 户外 (hùwài), meaning 'outdoor.' In daily life, it helps distinguish between activities done inside versus outside, and it is often used in weather forecasts, fitness contexts, and home-related discussions.