Definition:Ring with Unity

Definition

Let $\struct {R, +, \circ}$ be a non-null ring.

Then $\struct {R, +, \circ}$ is a ring with unity if and only if the multiplicative semigroup $\struct {R, \circ}$ has an identity element.

Such an identity element is known as a unity.

It follows that such a $\struct {R, \circ}$ is a monoid.

Also defined as

Some sources allow the null ring to be classified as a ring with unity.

Also known as

Other names for ring with unity are:

• Ring with a one
• Ring with identity
• Unitary ring
• Unital ring
• Unit ring

Some sources simply refer to a ring, taking the presence of the unity for granted.

On $\mathsf{Pr} \infty \mathsf{fWiki}$, the term ring does not presuppose said presence.

Also see

• Results about Rings with Unity can be found here.