DefinitionIn mathematics, field theory is a branch of abstract algebra which studies the properties of fields: sets endowed with two distinct operations of addition and multiplication, with more characteristic axioms (for instance, some fields having characteristic zero, some fields are locally compact, etc.). Field theory provides tools like fields, extensions of fields, algebraic extensions, Galois theory etc. that help to study properties of equations at the level of polynomial roots and other algebraic structures. Field theory is also used to study number theory, discussion of algebraic geometry, cryptography and theoretical physics. For example, the set of rational numbers Q forms a field under addition and multiplication, where every nonzero element has a multiplicative inverse.