Examine the shape to determine if it meets the criteria for a 3-dimensional shape: height, width and length. A picture of a 3-dimensional shape is 2-dimensional. The actual object we can touch is 3-dimensional.
Identify 3-dimensional shapes with curved surfaces. A sphere is a symmetrical, 3-dimensional figure shaped like a ball. It has no flat sides and no corners. Every point on the curved surface of the sphere is equidistant from the center of the sphere. A cone has a flat base that is circular in shape, topped with a rotated, right-angled triangle that results in a curved surface ending in a point, called a vertex.
Locate shapes with all flat surfaces (or faces). How many are there? A triangular prism is a 3-dimensional shape with three rectangular sides, and two ends that are triangles. A triangular prism has a triangular cross-section all the way along its length. Rectangular prisms have six faces that are all rectangles, with a cross-section that is a square. Cubes are equal in height, width and length. All six faces are square. Rectangular prisms and cubes, which are also prisms, are called cuboids.
Look for examples of 3-dimensional shapes in everyday life. Basketballs are spheres. Ice cream cones are cones. A pup tent is a triangular prism. A gift box is a rectangular prism. Dice are cubes.
Make paper examples of various 3-dimensional shapes. Adding a "hands-on" element to learning these shapes increases familiarity.