In mathematics, a field is a certain kind of algebraic structure. In a field, one can add (formula_1), subtract (formula_2), multiply (formula_3) and divide (formula_4) two numbers (with division only possible if formula_5 is non-zero). A field is a special ring in which division is possible. Both the set of rational numbers and the set of real numbers are examples of fields. One can also use the symbol formula_6 as a variable for a field.