A 4D shape, or four-dimensional shape, extends the concept of three-dimensional shapes by adding an additional dimension. While we can easily visualize 3D objects like cubes and spheres, 4D shapes exist beyond our direct perception. The most common example of a 4D shape is the tesseract, which is the four-dimensional equivalent of a cube. In mathematics and physics, 4D shapes are often used to explore complex concepts, such as spacetime in the theory of relativity. These shapes can be represented in 3D projections, allowing us to study their properties and relationships, even if we cannot fully visualize them in our three-dimensional world.