A well-designed object does what it is supposed to do. That is function, the purpose or role that a designed object is intended to serve. A knife cuts. A chair supports sitting. A website helps users find information or complete a task. Function is not the same as form, but the two are entangled. A chair that looks beautiful but collapses under weight fails its function. A website that loads quickly but confuses users also fails.

The relationship between form and function has been debated for over a century. The Bauhaus and modernist architects argued that form should follow function, meaning the shape of an object should be determined by its purpose. This led to clean, unornamented designs that prioritized use. Later critics noted that function is not always obvious or singular. A chair can be for sitting, for looking at, or for signaling status. A smartphone is a phone, a camera, a map, and a social space. Designers now often speak of affordances, the cues that suggest how an object should be used. A handle affords pulling. A button affords pressing.

Function in design

• Does it do what it is supposed to do?
• Is it easy to use without instructions?
• Does it hold up over time?
• Does it serve the user's actual needs?

Function is not the enemy of beauty. The best designs manage both, and neither is an afterthought.