A ratio, observed especially in the fine arts, between the two dimensions of a plane figure or the two divisions of a line such that the smaller is to the larger as the larger is to the sum of the two, a ratio of roughly three to five.
The ratio between two numbers a and b chosen such that the ratio of a to b is equal to the ratio of a+b to a. Its value is approximately 1.618. Shapes with proportions equal to the golden section are observed especially in the fine arts and in architecture, as between the two dimensions of a plane figure such as a rectangle. The ratio between consecutive numbers in a Fibonacci sequence approximates the golden section with increasing precision as the series progresses. Also called golden mean, golden ratio.
Two rectangles with the proportions of the golden section: the large rectangle, and the small one on the right inside it. The smaller rectangle has proportions a/b , equal to the proportions of the larger one, (a+b)/a .