As shown in the picture:

The specific method is: when parents buy small biscuits for their children, try to buy some with various shapes, and when the children eat, let the babies find round biscuits. Babies usually become more interested after receiving instructions from their parents. After the children can correctly find the round cookies, parents can let them find other shapes and deepen the training step by step. This not only allows children to understand shapes, but also gives them some fun. Extended information

A circle is a conic section obtained by a plane truncated cone parallel to the base of the cone.

A circle is a geometric figure. By definition, a compass is usually used to draw a circle. The diameter and length of the radius of the same circle are always the same. A circle has countless radii and countless diameters. A circle is an axially symmetrical and centrally symmetrical figure. The axis of symmetry is the straight line along which the diameter lies. At the same time, a circle is a "positive infinite polygon", and "infinity" is just a concept. The more sides a polygon has, the closer its shape, perimeter, and area are to a circle. Therefore, there is no real circle in the world. The circle is actually just a conceptual figure.