In product management, dependency refers to the relationship between tasks or features that rely on each other to be completed. It's like a domino effect, where one task must be finished before another can start. Dependencies can be internal, within your team, or external, relying on other teams or third-party services. For example, if you're developing a new feature that relies on a database update from the backend team, that database update becomes a dependency. Identifying and managing dependencies is crucial for planning and prioritizing work effectively.