/prəˈpɔːr.ʃən/

Proportion

noun · composition theory

What it is

Proportion concerns relationships, not measurements. A door is not "tall" in the abstract; it is tall in relation to the wall, the figure passing through it, and the panels within it. Change the surrounding parts and the same dimension reads differently. This is why proportion is described as ratio — it survives scaling. Enlarge a well-proportioned design to any size and the relationships, and the harmony, are preserved.

A continued proportion links three or more terms in a single chain, where the second term relates to the first as the third does to the second. The golden section is the special case where a : b = b : (a+b), so the whole relates to its larger part exactly as that part relates to the smaller. Proportional systems — the golden ratio, the modular scale, the root rectangles — are simply disciplined ways of holding such ratios constant across a whole work.

Etymology

The word comes from Latin proportio, "for its share," a translation of the Greek analogia used by Euclid. In the Elements (Book VI) Euclid defines a proportion as an equality of ratios and gives the "extreme and mean ratio" that later became the golden section. The Roman architect Vitruvius carried the idea into building, where proportion meant the commensurate relation of every member to the whole.

Examples in use

Le Corbusier built his Modulor as a proportional scale derived from the human body and the golden section, so that a wall, a door, and a handrail would all be members of one ratio family. György Doczi's The Power of Limits traces the same proportional relationships through pinecones, temples, and the human face.

In drawing, an instructor's note that a head is "out of proportion" is never about its absolute size — it is about its ratio to the shoulders or the length of the arm. Proportion is the comparative measurement that all sight-size and comparative-measurement methods exist to check.