A ring defined on a singleton set . The ring operations (multiplication and addition) are defined in the only possible way,
(1)
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and
(2)
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It follows that this is a commutative unit ring, where is the multiplicative identity. Of course, also coincides with the additive identity, i.e., it is the so-called zero element of the ring. For this reason, the trivial ring is often denoted and also called the zero ring. In fact, the subset is the only trivial subring of the ring of integers .
A unit ring is trivial whenever , since this equality implies that for all
(3)
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A trivial ring is a trivial module over itself.