👉 Rectilineal is a concept in geometry that describes a shape or object as having straight sides and no curved edges. This means that all sides of an object are equal in length, and there are no sharp corners or points on the object's surface. Rectilinear shapes can be classified into two categories: convex and concave. Convex shapes have their vertices at right angles to each other, while concave shapes have opposite sides that form a 90-degree angle with each other.