Forms are different shapes. They are 3 Dimensional Shapes. It is in other effects. Like 3-D. These are all the shapes the has forms:
1.Triangle - A 3 Shaped Form is : Pyramid
2.Square - Cube
Note : Most Rectangles are called Rectangular.
4.Circle is a sphere.
Note: Spheres,Triangular Prism,Cubes are solid figures. They can be classified. If they are Prisms or Solid Figures.They are different from each others.Some solids are not belong. These are called Inte-regular. or they are instictively. has 3 or 4 sides equally. So there are 7 shapes with figures. Oval,Triangle,Square,Rectangular and more.