Proportion in interior design refers to the relationship between the sizes of different elements within a space. It is important to consider proportion when designing a room in order to create a sense of balance and harmony. This can be achieved by ensuring that furniture, decor, and architectural elements are appropriately scaled to the size of the room and to each other. For example, a large sofa in a small room may feel overwhelming, while a small piece of art on a large wall may feel out of place. By paying attention to proportion, designers can create visually pleasing and comfortable spaces.