Definition:Algebraic Number

Definition
The set of algebraic numbers $\Bbb A$ is the subset of the complex numbers which are roots of polynomials with rational coefficients.

It can be seen that this definition of algebraic is consistent with the definition of algebraic over the field of rational numbers.

Examples
The algebraic numbers include:
 * The elements of the set of rational numbers $\Q$, since these are roots of linear polynomials.
 * $\sqrt 2$, since it is a root of $x^2 - 2$.
 * The golden section $\varphi$, since it is a root of $x^2 - x - 1$.
 * The complex number $0 + i$, since it is a root of $x^2 + 1$.