The **characteristic** of a ring is the least positive integer $n$ for which
\[
\underbrace{1+\cdots + 1}_n = 0,
\]
if such an $n$ exists, and $0$ otherwise. Equivalently, it is the exponent of the additive group of the ring.

The characteristic of a field $k$ is either $0$ or a prime number $p$, depending on whether the prime field of $k$ is isomorphic to $\Q$ or $\F_p$.

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- Last edited by John Jones on 2020-10-25 00:21:25

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