Classification of Binary Operations

🅟 Mar 15, 2026

  🅤 Jun 10, 2026

Definition 1.

Let $*$ be a binary operation on a set $X$. We define the following properties of $*$:

Property Condition
$A$ is closed under $*$ \(x * y \in A\)
Commutative \(x * y = y * x\)
Associative \(x * (y * z) = (x * y) * z\)
Idempotent \(x * x = x\)
Left-cancellative \(x * y = x * z \,\to\, y = z\)
Right-cancellative \(y * x = z * x \,\to\, y = z\)
Cancellative Left- and Right-cancellative
Central \((x * y) * (y * z) = y\)

If $+$ is another binary operation on $X$, we further define:

Property Condition
Left-distributive over $+$ \(x * (y + z) = x * y + x * z\)
Right-distributive over $+$ \((y + z) * x = y * x + z * x\)
Distributive over $+$ Left- and Right-distributive over $+$

The statements in the Condition column are meant to hold either for all $x\in X$; all $x$, $y\in X$; or all $x$, $y$, $z\in X$, accordingly.