What shape is used to represent a gateway in BPMN activity models?

In Business Process Model and Notation (BPMN), a gateway is represented by a diamond shape. This visual distinction is crucial in BPMN as the diamond indicates decision points in a process where the flow can diverge or converge based on certain conditions or events. Gateways can control the flow of a process, enabling branching, merging, and managing parallel activities. The use of the diamond shape is standardized in BPMN to maintain consistency and clarity when modeling business processes, making it easier for stakeholders to understand the decision logic involved.

The other shapes (triangle, rectangle, and circle) are used to represent different components in BPMN; triangles often signify exclusive gateways or specific types of decisions, rectangles represent tasks or activities, and circles typically denote events. The diamond's role as a gateway is integral to process modeling, highlighting its importance in BPMN as a tool for process management and analysis.