SOLID is an acronym representing five fundamental design principles for object-oriented programming that promote clean, maintainable, and extensible code:

• S - Single Responsibility Principle: A class should have only one reason to change
• O - Open/Closed Principle: Software entities should be open for extension but closed for modification
• L - Liskov Substitution Principle: Objects should be replaceable with instances of their subtypes
• I - Interface Segregation Principle: Clients should not depend on interfaces they don't use
• D - Dependency Inversion Principle: Depend on abstractions, not concretions

Benefits of following SOLID principles:

• Maintainability: Changes are localized and predictable
• Flexibility: Easy to extend and modify existing functionality
• Testability: Components can be tested in isolation
• Reusability: Well-designed components can be reused across different contexts
• Reduced coupling: Components are loosely connected and independently changeable
• Code clarity: Intent and structure are clearer and easier to understand