A dependency that must be satisfied when expected or it will cause the associated work to get blocked. Must-have dependencies must be included in the calculation of the number of dependencies in the dependency set of a work item.
For example, if the dependency set of a work item (e.g., an Epic) has three shared dependencies on other teams, and each of those dependencies absolutely must be satisfied or the work item would not be considered complete, then each of those shared dependencies is a must-have dependency and the cardinality of the dependency set is three.
In this example, if one of the shared dependencies was a nice-to-have dependency, then the cardinality of the dependency set would be two. Contrast with nice-to-have dependency.