Commutative ring facts for kids
In algebra, commutative ring is a set of elements in which you can add and multiply and have multiplication distribute over addition. An example of a commutative ring is the set of integers. If we add two integers, we get an integer and if we multiply two integers we get another integer. Moreover, multiplication distributes in the sense that if a, b, and c are integers, then c*(a+b)=ca+cb.
Images for kids

The cubic plane curve (red) defined by the equation y2 = x2(x + 1) is singular at the origin, i.e., the ring k[x, y] / y2 − x2(x + 1), is not a regular ring. The tangent cone (blue) is a union of two lines, which also reflects the singularity.

A pair of pants is a cobordism between a circle and two disjoint circles. Cobordism classes, with the cartesian product as multiplication and disjoint union as the sum, form the cobordism ring.
See also
In Spanish: Anillo conmutativo para niños