A unit is an element in a Ring that has a multiplicative inverse. If is an Algebraic Integer which divides every Algebraic Integer in the Field, is called a unit in that Field. A given Field may contain an infinity of units. The units of are the elements Relatively Prime to . The units in which are Squares are called Quadratic Residues.
See also Eisenstein Unit, Fundamental Unit, Prime Unit, Quadratic Residue