Zero element

In algebra, the term zero element is used with two meanings, both in analogy to the number zero.

• For an additively written binary operation, z is a zero element if (for all g)

z + g = g = g + z

i.e., it is the (unique) neutral element for this operation.

• For a multiplicatively written binary operation, a is a zero element if (for all g)

ag = g = ga

i.e., it is the (unique) absorbing element for this operation.

In rings (not only the real or complex numbers) 0 is the zero element in both senses.

In addition to these "two-sided" zero elements, (one-sided) left or right zero elements are also considered for which only one of the two identities is valid for all g.

One-sided zero elements need not be unique.