# Changes

technicality--both i and -i are square roots of -1

A '''complex number''' is a [[number]] composed of two parts - a [[Real number|real]] component and and [[Imaginary number|imaginary]] component, of the form <math>a + bi</math>, where ''a'' and ''b'' are real numbers and ~~''~~<math>i~~'' is the [[square root]] of negative ~~^2 = -1</math>.

Whereas the real numbers can be represented as all the possible points on an infinitely extended [[number line]], to represent all the complex numbers requires the use of a two dimensional coordinate system, usually with the real components on the horizontal axis (the ''abscissa'') and the imaginary components on the vertical axis (the ''ordinate'').