The word "Argand" has no direct synonyms as it is a proper noun that refers to the surname of a Swiss mathematician, Jean-Robert Argand. However, if we are to consider words that are related to Argand's contributions in mathematics, we could use terms such as complex number, imaginary number, or polar coordinates. These terms are associated with Argand's mathematical concepts and charts that were instrumental in representing complex numbers. Another word that comes to mind is "plane", as in the Argand plane, which is a mathematical way of visualizing complex numbers as points on a two-dimensional graph. Ultimately, while there is no exact synonym for Argand, we can use related terms that are associated with his important contributions to mathematics.