A '''ring''' in [[mathematics]] is a set ''R'' equipped with two [[binary]] [[operation]]s, usually called addition and multiplication, satisfying that
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A '''ring''' in [[mathematics]] is a set ''R'' equipped with two [[binary]] [[operation]]s, usually called addition and multiplication, satisfying that
'''1.''' ''R'' with addition is a [[commutative]] [[group]];
'''1.''' ''R'' with addition is a [[commutative]] [[group]];
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'''2.''' ''R'' with multiplication is a [[semigroup]];
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'''2.''' ''R'' is closed under multiplication;
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'''3.''' multiplication [[distribute]]s over addition.
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'''3.''' Multiplication is [[associative]];
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'''4.''' Multiplication [[Distributivity|distribute]]s over addition.
==Remarks==
==Remarks==
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A '''ring with unit''' is a ring for which multiplication has a [[neutral element]].
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A '''ring with unity''' is a ring for which multiplication has a [[neutral element]].
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A '''commutative ring''' is a ring in which multiplication is commutative.
A '''division ring''' is a ring such that ''R'' with multiplication is a (not necessarily [[commutative]]) [[group]].
A '''division ring''' is a ring such that ''R'' with multiplication is a (not necessarily [[commutative]]) [[group]].