An intentional feature is created by making a necessary physical property.
Consider a coffee mug: You make a handle intentionally on a coffee mug to hold it. The handle is an intended feature. It is deliberately adaptive toward a known and desired end (drinking hot coffee without burning ones hands). Developing this feature is change-in-degree — a quantitative change (e.g. one could make the handle thicker or thinner, longer or shorter, more embellished or less — but in every case it is just a variation of the existing logic of a handle and its purpose).
See also: Things
