SOLID Principles

SOLID is an acronym for five object-oriented design principles that make software easier to understand, maintain, and extend.

Letter	Principle	One-liner
S	Single Responsibility	A class should have only one reason to change
O	Open / Closed	Open for extension, closed for modification
L	Liskov Substitution	Subtypes must be substitutable for their base types
I	Interface Segregation	Clients should not depend on interfaces they don't use
D	Dependency Inversion	Depend on abstractions, not concretions

Design Patterns & Principles