Cloud Elasticity or Scalability, Whats the Difference?

I have heard and read at lot of places about Elasticity and Scalability of the cloud. In a discussion the point came across that what actually is the difference between Elasticity and the Scalability, when it comes to cloud.

I myself could not find the demarcation, so I searched around the web. But to my surprise lot of people on the articles conviniently use Elasticity and Scalability interchangeably in relation the cloud. After reading around I could not find the answer, so I though to put my own thoughts since I dont agrre that both is same and let people decide if my understanding is right or not.

What means by Elasticity in relation to cloud is that it could scale up or down the infrastructure to meet the requirement. Elasticity is about instantly bringing you the necessary resource when you need it and instantly decommission them when you don't need it. Elasticity is an important feature of the cloud offering as you are charged only during the time when you are using it.

Scalability in terms of the application architecture means that how well an application could gracefully handle the increased load. One of the ways to achieve Scalability is adding additional hardware. So to introduce additional hardware either we go the manual intervention way or the automatic provisioning. The automatic provisioning is the elastic nature of the platform. Not only does the elastic platform has the capability of adding additional hardware but scaling down when it not required. With the elasticity of the platform, your application should have the capability to use the additional or reduced hardware.

Hense Elasticity makes sense for the platform and Scalability makes sense for the application. A scalable application only can best use the elastic platform.