When a merchant sells goods, the Uniform Commercial Code adds an implied warranty that they are “merchantable.” This applies when the seller deals in goods of that kind. Section 2-314 says such goods must be “fit for the ordinary purposes for which such goods are used.”
Cornell Law School’s legal dictionary explains the standard. Merchantable goods “need not be outstanding or superior quality, they need only be fit for the ordinary purpose for which they are used.” In everyday terms, a toaster bought in a store must toast. It does not have to be the best toaster on the market.
Section 2-315 adds a separate warranty for a particular purpose. It applies only when the seller has reason to know that purpose and the buyer relies on the seller’s judgment.