“Golden Section: (golden mean) A geometrical proportion known at least since Euclid and regarded as a universal law of the harmony of proportions in both art and nature. The common formula is: to divide a finite line so that the shorter part is to the longer part as the longer part is to the whole.”
Excerpted from: Diamond, David G. The Bulfinch Pocket Dictionary of Art Terms. Boston: Little Brown, 1992.