Afferent coupling (Ca)
Alternative name for Fan-in and fan-out.
Afferent coupling, denoted Ca, counts distinct in-scope architecture units with a direct dependency into the selected package or unit. It is the formal term for what AtlasArc calls fan-in. A high Ca indicates many direct dependents and can make changes more consequential; it does not prove that every dependency uses public API or that every change affects every dependent.