Which cloud concept describes the ability to automatically acquire resources when needed and release them when they are no longer required?

Elasticity is the ability of a system to automatically scale computing resources up or down based on demand. This means resources are provisioned when needed and de-provisioned when not, optimizing cost and performance. Availability refers to a system's ability to remain operational and accessible for a specified period. Durability is the long-term preservation of data, ensuring it is not lost or corrupted. Reliability is the probability that a system will perform its intended function without failure for a specified period under stated conditions. While related, only elasticity specifically addresses the automatic acquisition and release of resources based on fluctuating demand.