Price Discrimination Terminology. Last week at the I.O. workshop someone had a good idea for replacing the old 1st, 2nd, 3rd degree price discrimination terminology. Exogenous-feature price discrimination is based on things the buyer can't change that the seller observes, such as his age. Endogenous-feature price discrimination is based on things the buyer can change, such as the quantity he buys or the quality he buys.