Form Follows Function
A principle which says that the shape of a building or object should primarily relate to its intended function or purpose.
Origin
American architect Louis Sullivan — known as the "father of skyscrapers" — published the phrase in his 1896 essay "The Tall Office Building Artistically Considered" in Lippincott's Magazine. His actual words were "form ever follows function," though the simpler version stuck. Sculptor Horatio Greenough had anticipated the idea decades earlier, criticizing American architecture's imitation of European styles. The principle became a battle cry of the Modernist movement in architecture and design after the 1930s.
Everyday Use
A coffee mug has a handle because you need to grip something hot — the form serves the function. This principle shows up in everything from smartphone design to office layouts: the best designs start with what something needs to do, not what it should look like. When form and function align, the result feels intuitive; when they don't, you end up with beautiful objects nobody can figure out how to use.