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# Prime elements

A **prime element** of a domain is an element which is neither zero nor a unit divisible only by units and associates and which also satisfies the following condition: if , where and are also in the same domain, then either or , maybe both; but if neither of those holds true, then may be irreducible but it is not prime. In fact, if the domain is not a unique factorization domain, it does not have prime elements though it may have irreducible elements.

For example, in (see: Gaussian integers), we see that and that . Though , this does not detract from the fact that is a prime element of .

Although 2 is irreducible in , it is not prime. For example, ,^{[1]} but and either. Note that 6 has two factorizations into irreducibles: .

## Notes

- ↑ Ian Stewart & David Tall,
*Algebraic Number Theory and Fermat's Last Theorem*, 3rd Ed. Natick, Massachusetts: A. K. Peters (2002): 87