This is the 2801st most frequent Chinese word.
室內
Indoor.
The word "室內" here means "interior" and is used to describe design specifically related to internal spaces within buildings.
室內设计是一门艺术与实用相结合的学科。
Interior design is a discipline that combines art and practicality.
"室內" in this sentence means "indoors" and is used to contrast activities that occur inside versus outdoors.
在室內进行锻炼可以避免天气对运动的影响。
Exercising indoors can avoid the effects of weather on physical activity.
Here, "室內" signifies the indoor setting and is used to specify the type of furniture appropriate for inside spaces.