Discrete mathematics, what is a ring? Please give an example.

It suddenly occurred to me that it might mean this: What ring is in it?

Unary: If the element E in A is both a left unary and a right unary, it is called the unary of operation ☆ in A. ..

Obviously, for any x ∈ A, there is e ☆ x = x ☆ e = x

ring

Set < a, △, ☆ > Is an algebraic system with two binary operations △ and *, if applicable:

①& lt； I. △ > It is an abelian group;

②& lt； Answer, ☆ > Is a semigroup;

(3) Operation ☆ Operation△ is distributable, namely:

a ☆ (b △ c) = (a ☆ b) △ (a ☆ c)

(b △ c) ☆ a = (b ☆ a) △ (c ☆ a)

Then it's called

What rings are included:

Let v =

(x☆y)☆z = x☆(y☆z)

Then v is called semigroup.