When is supply said be elastic?

Supply of a good is elastic when a small increase in price leads to a large increase in quantity supplied.

A sociologist would explain this phenomena this way: This occurs because the good is easy to make - no complicated processes, small start-up capital, no need for skilled labour, rare-metals, anybody can do it! Thus, when the price increases by a little, many more new producers find that they can now produce the good (because now they are willing to accept the price on the market).