![Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors). Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors).](https://www.uml-diagrams.org/use-case-diagrams/use-case-diagram-elements.png)
Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors).
![Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors). Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors).](https://www.uml-diagrams.org/use-case-diagrams/business-use-case-diagram-elements.png)
Use case diagrams are UML diagrams describing units of useful functionality (use cases) performed by a system in collaboration with external users (actors).
![UML use case diagram. H = hospital, P = primary care; number sign =... | Download Scientific Diagram UML use case diagram. H = hospital, P = primary care; number sign =... | Download Scientific Diagram](https://www.researchgate.net/publication/332145129/figure/fig1/AS:743216374632449@1554208000412/UML-use-case-diagram-H-hospital-P-primary-care-number-sign-countries-where-the.jpg)