In order to comprehend the ontological construction below, please refer to the respective posts for all notions in italic.
Normal price elasticity describes the comparative adjustments of the price and the quantity of a commodity. Changes in the supply or in the demand of commodities are just proportional to the price alterations. As any amendment in the price of a product affects its productive consumption and, through it, corrects its quantity. In ever approximated market equilibrium, a change in the price of an economic good is followed by a change in the quantity of that good. It is a midpoint between perfect price elasticity and perfect price inelasticity leading to commodity substitution effect.
Historical Backdrop
• ALFRED MARSHALL Principles of Economics: elasticity of demand and elasticity of supply.