What are the criteria for goods being considered inelastic?

Question

What are the criteria for goods being considered inelastic?

Answer 1

Goods and services for which no substitutes exist are generally inelastic. ...The price elasticity of demand, a measure of the responsiveness of quantity demanded to a price change, may cause a change in price to have a small or large impact on quantity demanded. Inelastic goods such as gasoline are still purchased in approximately the same quantity even when prices rise. Elastic goods such as restaurant meals, movie tickets, and luxury items usually follow the law of demand and will see a drop in quantity demanded when prices rise