SOLID principles are key to creating flexible and maintainable object-oriented software: - S - Single Responsibility Principle: A class should have only one reason to change, meaning it should only have one job or responsibility. - O - Open/Closed Principle: Software entities should be open for extension but closed for modification. This means you should be able to add new functionality without changing existing code. - L - Liskov Substitution Principle: Objects of a superclass should be replaceable with objects of a subclass without affecting the correctness of the program. - I - Interface Segregation Principle: No client should be forced to depend on methods it does not use. It's better to have many specific interfaces than one general-purpose interface. - D - Dependency Inversion Principle: Depend on abstractions, not on concretions. High-level modules should not depend on low-level modules; both should depend on abstractions. Understanding and applying these principles can lead to more robust, scalable, and maintainable code in software development.