What element of Revit allows for defining shared parameters across different family types?

The element of Revit that allows for defining shared parameters across different family types is shared parameters. Shared parameters are a specific type of parameter that can be used throughout a project across multiple families, making them invaluable for maintaining consistency and facilitating data sharing among various Revit components.

When you create a shared parameter, you can assign it to several different family types, ensuring that all elements that require that specific data field can access the same parameter. This is particularly useful for creating schedules, tagging elements, or ensuring compliance with project standards, as it enables a unified approach to data management in a project.

In contrast, project templates provide predefined settings but do not specifically manage shared parameters. Family types are used to define variations within a family but do not inherently allow for sharing parameters across different families. Element properties reflect the characteristics of individual elements and are typically not used for sharing parameters between multiple family types.