TL;DR: DIP (Dependency Inversion Principle): High-level modules should not depend on low-level modules; both depend on abstractions. DI (Dependency Injection): A technique to supply dependencies from outside a class, improving testability and flexibility. IoC (Inversion of Control): A broader concept where control of object creation and dependency resolution is delegated to a container or framework. Together, they enable decoupled, maintainable, and testable applications. DIP is a design principle, DI is a pattern, IoC is the overarching concept. I bombed this question in an interview once. ...