Form (Ever) Follows Function.

This is the famous axiom about architectural modernist movement. It has become a law, Credo, Dictum, and a principle to students of architecture and design. To practicing architects and Designers( industrial and ICT base). The principle in which most modern architectural designs are govern. This is a principle which purports that the shape of a building or an object is determined by it intended usage, purpose or function. It implies the "end"(function) should determined the "means" (form).

The Origins 

The phrase "form follows function" has wrongly been attributed to Horatio
Greenough, who some believed did works using similar phrase sometimes before it became popular.

The phrase was coin by American Architect and supposedly father of sky scrappers Louis H. Sullivan. In his watershed essay of 1896 titled “The Tall Office Building Artistically Considered ,” Sullivan wrote:

"It is the pervading law of all things organic and inorganic, of all things physical and metaphysical, of all things human and all things superhuman, of all true manifestations of the head, of the heart, of the soul, that the life is recognizable in its expression, that form ever follows function. This is the law."

You can read the full text here.

Looking back to the time when this essay was delivered, the technology, taste and nature of the economy was different from what it is today, this factors contributed to the need of a new kind of structure and buildings. As  a monarch of modernity, Sullivan seek for a shape that is appropriate, one defined not by the past or antecedent but by function , a building that will deviate from the Roman-Greco style prevalent at the time. There came the birth of modernity(Architectural).

Proponents

There is a strong list of disciples and legends of the noble field who had adopted Form follow function as their core mantra, they include Louis Sullivan,   Adolf Loos, Mies Van der Rohe, Frank Lloyd Wright, Le Corbusier, Walter Gropius, Horatio Greenough  and many more.

Interpretation of form follow function.

There are mainly two explanations to this famous dictum "form follows function".

•Descriptive: beauty results from purity of function;

•Prescriptive: aesthetic considerations in
design should be secondary to
functional considerations.

Since after a year after Sullivan's essay a lot of architect and similar field have written about the phrase dissecting and criticising it. That not withstanding a lot of students of architecture and designing and professional architects and general fields of design have worn this credo as a batch to be proud of to times indefinite.