SOLID

An acronym for 5 design principles in software engineering.

- Definition

In software engineering, SOLID is an acronym for five design principles intended to make object-oriented designs more understandable, flexible, and maintainable.

- Breakdown of the Acronym

Letter	Meaning
S	The Single Responsibility principle says that Every class should have only one responsibility.
O	The Open-Closed principle says that Software entities should be open for extension, but closed for modification.
L	The Liskov Substitution principle says that Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it. .
I	The Interface Segregation principle says that Clients should not be forced to depend upon interfaces that they do not use".
D	The Dependency Inversion principle instructs you to Depend upon abstractions, not concretions.

Although the SOLID principles apply to any object-oriented design, they can also form a core philosophy for methodologies such as agile development or adaptive software development.