Conceptual contours emerge when domain knowledge is spread throughout the code to a sufficient degree. In OOP, this can be achieved by carefully following the principles of DDD.

In FP, conceptual contours emerge more readily, once again due to the declarative and side-effect-free nature of the paradigm. Specifically, clients of the domain model can rely on cohesive functionality attained with composition and yet still have access to constituents without breaking encapsulation.