Roughness refers to the texture of a surface that is not smooth. It can be felt when you run your fingers over materials like sandpaper or rock. Rough surfaces can create friction, which is why walking on a rough path can be more challenging than walking on a smooth one. In nature, roughness is often found in landscapes, such as mountains or forests, where uneven ground and rugged features create a sense of wildness. This texture can also be seen in everyday objects, like a tree bark or a brick wall, adding character and interest to their appearance.