client

This term carries a professional weight that distinguishes it from customer. While a customer typically makes a one-off purchase of a product, a client enters into a sustained, fiduciary, or advisory relationship. It implies a higher level of trust and a personalized service tailored to specific needs, commonly found in legal, accounting, or creative agency contexts.

In the digital realm, the word shifts from a human relationship to a technical architecture. It describes a subordinate system that requests data or resources from a more powerful central hub. This relationship is purely functional and transactional, devoid of the emotional or professional loyalty associated with the human usage.