The norm of an element in mathematics, particularly in the context of algebraic number theory and field theory, is a function that maps elements of a field extension to the base field, providing a measure of the 'size' or 'magnitude' of the element. It plays a crucial role in understanding the structure of number fields, aiding in the classification of algebraic integers and the analysis of field extensions.
Units in number fields are elements that have a multiplicative inverse within the field, forming a group under multiplication known as the unit group. Understanding the structure of this group is crucial for solving Diophantine equations and studying algebraic integers, as it reveals deep insights into the arithmetic properties of the field.