What is a design pattern?
For the most part, ideas are only applicable in one place. Adding peanut butter is really only a great idea in cooking and not in sewing. However, from time to time, it is possible to find applicability for a great idea outside of its original purpose. This is the story behind design patterns.
In 1977, Christopher Alexander, Sara Ishikawa, and Murray Silverstein authored a seminal book on what they called design patterns in urban planning called A Pattern Language: Towns, Buildings, Construction, Oxford.
The book described a language for talking about the commonalities of design. In the book, a pattern is described by Christopher Alexander as follows:
The elements of this language are entities called patterns. Each pattern ...