In mathematics, an algebra's unital (some authors say unitary) if it contains a multiplicative identity element (or unit), for example an element 1 with the property 1x = x1 = x for all elements x of the algebra. This's equivalent to saying that the algebra's a monoid for multiplication. As in any monoid, such a multiplicative identity element's then unique. Most associative algebras considered in abstract algebra, for instance group algebras, polynomial algebras and matrix algebras, are unital,… (More on Unital)