# Invertibility Is a property of binary operations that is satisfied if, for every element $a$, there exist two elements $b$ and $c$ such that: $ a \circ b = c \circ a = a_0 $ (where $a_0$ is the [[Identity|Identity Element]] of the binary operation). If the operation is also [[Commutativity|commutative]], $a$ and $b$ are the same. Invertibility is closely related to [[Divisibility]]. If an operation is divisible, and also has an [[Identity|Identity Element]], it is considered invertible.