# Absorbing element

In algebra, an absorbing element or a zero element for a binary operation has a property similar to that of multiplication by zero.

Formally, let $\star$ be a binary operation on a set X. An element O of X is absorbing for $\star$ if

$O \star x = O = x \star O \,$

holds for all x in X. An absorbing element, if it exists, is unique.