Polymorphism: Polymorphism allows objects of different classes to be treated as instances of their common superclass or interface. This promotes flexibility and code reuse by allowing different implementations to be used interchangeably.
Abstract Class: An abstract class is similar to an interface but can also contain method implementations along with method declarations. It serves as a partial blueprint and cannot be instantiated directly.
API (Application Programming Interface): APIs are sets of rules and protocols that allow different software systems to communicate with each other. They provide well-defined interfaces for accessing functionality provided by libraries or frameworks.