Bands

A band is a semigroup B = (B,·) such that · is idempotent: xx = x.

Let B and C be bands. A morphism from B to C is a function h : B→C that is a homomorphism: h(xy) = h(x)h(y).

Classtype	variety
Equational theory	decidable in polynomial time
Quasiequational theory
First-order theory
Locally finite	yes
Residual size
Congruence distributive	no
Congruence modular	no
Congruence n-permutable	no
Congruence regular	no
Congruence uniform	no
Congruence extension property	no
Definable principal congruences
Equationally definable principal congruences
Amalgamation property	no
Strong amalgamation property	no
Epimorphisms are surjective

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