Scalability is the property of a system to handle a growing amount of work by adding resources to the system.
In computing, scalability is a characteristic of computers, networks, algorithms, networking protocols, programs and applications.
Capability of a product to handle growing or shrinking workloads or the ease with which the product’s capacity can be adapted to handle variability
This specifies the expected increases in size that the product must be able to handle. As a business grows (or is expected to grow), our software products must increase their capacities to cope with the new volumes.