form follows function

The idea that good form results from selecting for good function. if the thing does what it needs to, it will looks and feel like it does.

The Von Karman ogive is an example of this.

The Feynman-Tufte Principle - Scientific American

Related: tool implies function. The idea that tools are objects selected to have certain functions, so their use probably constrains the action they are being used for.

Every word used above could stand to be defined and explored a little better.

If you're using an object of some kind to perform an action, the nature of the object makes it more or less useful for that action. Taken across actions, we can characterise the object as having a function.