A large-scale distributed computing paradigm that is driven by economies of scale, in which a pool of abstracted, virtualised, dynamically- scalable, managed computing power, storage, platforms and services are delivered on demand to external customers over the Internet. 

Key elements:

• it is a specialised distributed computing paradigm; 
  
• it is massively scalable; 
  
• it can be encapsulated as an abstract entity that delivers different levels of services to customers outside the Cloud; 
  
• it is driven by economies of scale; and, 
  
• the services can be dynamically configured (via virtualisation or other approaches) and delivered on demand.