Scalability

n. ability to adjust configuration and size to fit new conditions; (Computers) ability to change the scaling of an application; ability to expand the capabilities of a computer; ability to change the size of a font or picture

In telecommunications and software engineering, scalability is a desirable property of a system, a network, or a process, which indicates its ability to either handle growing amounts of work in a graceful manner, or to be readily enlarged. For example, it can refer to the capability of a system to increase total throughput under an increased load when resources (typically hardware) are added. An analogous meaning is implied when the word is used in a commercial context, where scalability of a company implies that the underlying business model offers the potential for economic growth within the company.
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Noun
1. the quality of being scalable
(hypernym) quantifiability, measurability

How well a solution to some problem will work when the size of the problem increases.
For example, a central server of some kind with ten clients may perform adequately but with a thousand clients it might fail to meet response time requirements. In this case, the average response time probably scales linearly with the number of clients, we say it has a complexity of O(N) ("order N") but there are problems with other complexities. E.g. if we want N nodes in a network to be able to communicate with each other, we could connect each one to a central exchange, requiring O(N) wires or we could provide a direct connection between each pair, requiring O(N^2) wires (the exact number or formula is not usually so important as the highest power of N involved).
(1995-03-29)

the ability of a idea, business, product or service to continue to function well regardless of how large it grows.