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Let be a semigroup. An idempotent is primitive if for every other idempotent ,

A semigroup (without zero) is completely simple if it is simple and contains a primitive idempotent.
A semigroup is completely 0-simple if it is 0-simple and contains a primitive idempotent.
Completely simple and completely 0-simple semigroups maybe characterised by the Rees Theorem (to appear).
Note:
A semigroup (without zero) is completely simple if and only if it is regular and weakly cancellative.
A simple semigroup (without zero) is completely simple if and only if it is completely regular.
A 0-simple semigroup is completely 0-simple if and only if it is group-bound.
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