Meaning of Argand diagram

Ar'gand di"agram

Pronunciation: [key]
— Math. Math.
  1. a Cartesian coordinate system consisting of two perpendicular axes for graphing complex numbers, the real part of a number being plotted along the horizontal axis and the imaginary part along the vertical axis. Cf. imaginary axis, real axis.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.