Definition:Radical of Ideal of Ring/Definition 1

Definition
Let $A$ be a commutative ring with unity.

Let $I$ be an ideal of $A$.

The radical of $I$ is the ideal of elements of which some power is in $I$:
 * $\map \Rad I := \set {a \in A: \exists n \in \N : a^n \in I}$

Also see

 * Equivalence of Definitions of Radical of Ideal of Ring