When a system design can expand to meet future business requirements and volumes, it is known to be:

The term that best describes a system design capable of expanding to meet future business requirements and volumes is "scalable." Scalability refers to the ability of a system to handle a growing amount of work or its potential to accommodate growth. This can be achieved either by expanding the system's capabilities (such as increasing hardware resources) or by optimizing software performance to manage increases in demand without loss of efficiency.

When a system is designed with scalability in mind, it can adapt to various levels of usage, whether that means accommodating more users, processing larger volumes of data, or integrating new functionalities as needed without requiring a complete redesign. This characteristic is especially crucial in environments where business demands fluctuate or grow over time, enabling organizations to remain agile and responsive.

Other terms like "flexible," "robust," and "dynamic" imply different qualities. Flexibility generally refers to the ease with which a system can adapt to changes, not necessarily related to capacity. Robustness hints at the system's strength and ability to handle errors or challenges, while dynamics suggest the system's ability to change over time, rather than focusing specifically on growth or capacity. Therefore, scalability is the most appropriate term in this context.