A domain owns its vocabulary. It never borrows from its callers
Manifesto line eight — domains organize responsibilities and their vocabulary — carries a consequence that is easy to miss.
The vocabulary a domain uses to describe its work is not negotiable with its callers. A domain that names things the way its consumers name them loses its own identity. It becomes pulled in as many directions as it has callers — each one with its own terminology, its own assumptions, its own way of describing what they want.
The rule is simple: callers adapt to the domain's vocabulary at the boundary. The domain never adapts to theirs.
This is not bureaucratic stubbornness. It is the mechanism that keeps a domain's model coherent over time. The moment a domain starts renaming its concepts to suit a particular caller, it has two models — one for that caller and one for itself. Eventually it has as many models as it has callers, and none of them are the one true model of how the domain actually works.
A domain that owns its vocabulary owns its identity. A domain that surrenders its vocabulary has no boundary left to defend.
Name things precisely. Name them on your own terms. Hold the line.