algebraic number

Written and fact-checked by The Editors of Encyclopaedia Britannica

Article History

Key People:: Leopold Kronecker

Related Topics:: number; algebraic integer

See all related content

algebraic number, real number for which there exists a polynomial equation with integer coefficients such that the given real number is a solution. Algebraic numbers include all of the natural numbers, all rational numbers, some irrational numbers, and complex numbers of the form pi + q, where p and q are rational, and i is the square root of −1. For example, i is a root of the polynomial x² + 1 = 0. Numbers, such as that symbolized by the Greek letter π, that are not algebraic are called transcendental numbers. The mathematician Georg Cantor proved that, in a sense that can be made precise, there are many more transcendental numbers than there are algebraic numbers, even though there are infinitely many of these latter.

This article was most recently revised and updated by William L. Hosch.