Final answer:
The atrium was the primary space in an aristocratic domus for receiving clients, highlighting the patron's status and used for official business.
Step-by-step explanation:
The space in an aristocratic domus used primarily for receiving clients was the atrium. This area was intricately designed to demonstrate the wealth and power of the patron of the house. It was customary for the paterfamilias to conduct official business and meet with his clients here, underscoring their position within the social hierarchy. The atrium often featured decorative elements such as colorful mosaics and was positioned in a way that accentuated the grandeur of the house upon entry.