Algebraic number

Complex number that is a root of a non-zero polynomial in one variable with rational coefficients
Algebraic numbers colored by degree (blue = 4, cyan = 3, red = 2, green = 1). The unit circle is black.

has a unique real root that cannot be expressed in terms of only radicals and arithmetic operations.

Algebraic numbers colored by leading coefficient (red signifies 1 for an algebraic integer)