# Prime ring

In abstract algebra, a nonzero ring R is a prime ring if for any two elements a and b of R, arb = 0 for all r in R implies that either a = 0 or b = 0. This definition can be regarded as a simultaneous generalization of both integral domains and simple rings.

Prime ring can also refer to the subring of a field determined by its characteristic. For a characteristic 0 field, the prime ring is the integers, for a characteristic p field (with p a prime number) the prime ring is the finite field of order p (cf. prime field).[1]

## Equivalent definitions

A ring R is prime if and only if the zero ideal {0} is a prime ideal in the noncommutative sense.

This being the case, the equivalent conditions for prime ideals yield the following equivalent conditions for R to be a prime ring:

• For any two ideals A and B of R, AB={0} implies A={0} or B={0}.
• For any two right ideals A and B of R, AB={0} implies A={0} or B={0}.
• For any two left ideals A and B of R, AB={0} implies A={0} or B={0}.

Using these conditions it can be checked that the following are equivalent to R being a prime ring:

• All right ideals are faithful modules as right R modules.
• All left ideals are faithful left R modules.

## Examples

• Any domain is a prime ring.
• Any simple ring is a prime ring, and more generally: every left or right primitive ring is a prime ring.
• Any matrix ring over an integral domain is a prime ring. In particular, the ring of 2-by-2 integer matrices is a prime ring.

## Notes

1. ^ Page 90 of Lang, Serge (1993), Algebra (Third ed.), Reading, Mass.: Addison-Wesley Pub. Co., ISBN 978-0-201-55540-0, Zbl 0848.13001