Elasticity

What Does Elasticity Mean?
A measure of a variable's sensitivity to a change in another variable. In economics, elasticity refers the degree to which individuals (consumers/producers) change their demand/amount supplied in response to price or income changes.

Calculated as:

Investopedia explains Elasticity
Elasticity is used to assess the change in consumer demand as a result of a change in the good's price. When the value is greater than 1, this suggests that the demand for the good/service is affected by the price, whereas a value that is less than 1 suggest that the demand is insensitive to price. 

Businesses often strive to sell/market products or services that are or seem inelastic in demand because doing so can mean that few customers will be lost as a result of price increases.