In software engineering, structural design patterns are design patterns that ease the design by identifying a simple way to realize relationships among entities.

Examples of Structural Patterns include:

• Adapter pattern: 'adapts' one interface for a class into one that a client expects
  • Adapter pipeline: Use multiple adapters for debugging purposes.^[1]
  • Retrofit Interface Pattern:^[2][3] An adapter used as a new interface for multiple classes at the same time.
• Aggregate pattern: a version of the Composite pattern with methods for aggregation of children
• Bridge pattern: decouple an abstraction from its implementation so that the two can vary independently
  • Tombstone: An intermediate "lookup" object contains the real location of an object.^[4]
• Composite pattern: a tree structure of objects where every object has the same interface
• Decorator pattern: add additional functionality to an object at runtime where subclassing would result in an exponential rise of new classes
• Extensibility pattern: a.k.a. Framework - hide complex code behind a simple interface
• Facade pattern: create a simplified interface of an existing interface to ease usage for common tasks
• Flyweight pattern: a large quantity of objects share a common properties object to save space
• Marker pattern: an empty interface to associate metadata with a class.
• Pipes and filters: a chain of processes where the output of each process is the input of the next
• Opaque pointer: a pointer to an undeclared or private type, to hide implementation details
• Proxy pattern: a class functioning as an interface to another thing

• Abstract Document Pattern
• Behavioral pattern
• Concurrency pattern
• Creational pattern

Wikimedia Commons has media related to Structural software design patterns.