Elasticity is the ability of an IT infrastructure to quickly expand or cut back capacity and services without hindering or jeopardizing the infrastructure's stability, performance, security, governance or compliance protocols.
Although the words scalability and elasticity are sometimes used as synonyms, scalability is more often used to describe the ability a system has to successfully cope with an expanding workload, while elasticity implies that the system is also capable of decommissioning capacity or resources when they are no longer needed.
In this sense, elasticity is a synonym for adaptability. Attributes of an elastic IT environment include the environment's ability to expand and contract in response to business needs. In a cloud service environment, elasticity may also imply that the ability the service can expand and contract in real time, using service level agreements (SLAs) to make changes autonomically, instead of relying on human administrators.
Customers for cloud services that are described as being elastic pay only for the capacity and resources they use.