👉 In mathematics, a sub-surface is an area that lies below or on top of another surface. These are essential to understanding how two different geometric shapes can intersect each other and interact with one another in space. For instance, a solid object like a ball may be defined as a subset of its own surface. For example, consider the solid sphere \(S\) and its boundary \(\partial S\), which is the set of points on the sphere that are at a distance less than or equal
