To translate one interface for a class into a compatible interface. An adapter allows classes to work together that normally could not because of incompatible interfaces by providing it's interface to clients while using the original interface.

Examples

DB Client libraries adapter
using multiple different webservices and adapters normalize data so that the outcome is the same for all

UML Diagram

![Alt Adapter UML Diagram](https://rawgithub.com/jtwebb/DesignPatternsPHP/blob/master/Structural/Adapter/uml.svg)