Two goods are defined as “close substitutes” if they exhibit a high cross-elasticity and “weak substitutes” if they exhibit a marginal cross-elasticity. Goods are defined as “perfect substitutes” if the consumer receives the exact same utility from the two goods. Therefore, consumer preference plays a part in the definition of a perfect substitute. Coke and Pepsi may be perfect substitutes to one consumer because he receives the same satisfaction from both. However, a different consumer may define Coke and Pepsi as near-perfect substitutes because he believes one tastes better than the other.