What does an elasticity measure of -.2 mean?

This video goes over the intuitive explanation of how to interpret different elasticity measures. It also discusses the intuition behind the different elasticity measures (such as price elasticity of demand, income elasticity of demand, cross price elasticity of demand, and price elasticity of supply). Finally, it discusses the key critical values that could possibly change the relative interpretations depending on which elasticity measure it is focusing on. More information is available at:
www.freeeconhelp.com/2011/06/...