The set of idempotents in a semigroup is a biordered set and every biordered set is the set of idempotents of some semigroup. A regular biordered set is...

pressed. Which is not idempotent, because each press adds further delay. Biordered set Closure operator Fixed point (mathematics) Idempotent of a code Idempotent...

have sometimes been considered by various authors. Absorbing element Biordered set Compact semigroup Empty semigroup Generalized inverse Identity element...

: 81  Semiautomaton Krohn–Rhodes theory Symmetric inverse semigroup Biordered set Special classes of semigroups Composition ring Dominique Perrin; Jean...

hold. eventually regular semigroup E-dense (aka E-inversive) semigroup Biordered set Special classes of semigroups Nambooripad order Generalized inverse...

various applications in theoretical computer science. Orthodox semigroup Biordered set Pseudogroup Partial symmetries Regular semigroup Semilattice Green's...

of the set of idempotents in a regular semigroup. He called a set having this structure a biordered set. "The axioms defining a biordered set are quite...