From The Business of Consuming section of How You Can Avoid Legal Land Mines by Joseph S. Lyles (2003)

Fortunately, consumers are not solely dependent on makers of products to provide them with warranties for new items they purchase. All purchased goods come with one or more unwritten warranties called implied warranties.

There are two basic types of implied warranties: the warranty of merchantability and the warranty of fitness for a purpose. These warranties, or promises, exist by operation of law and are in addition to any written warranty that the manufacturer may provide. Such a written warranty is called an express warranty.

If a manufacturer wants to disclaim or deny the existence of a warranty, it must do so in bold-face type and must follow other specific legal requirements. However, a manufacturer cannot disclaim the implied warranty of merchantability.

Merchantability simply means that a product is what it purports to be. In other words, if it looks like a hammer and is sold as a hammer, it very well better be able to drive a nail. The warranty of merchantability seems obvious in the case of something simple like a hammer, but in the case of something complex, like a computer program, it is much more complicated.

The warranty of fitness for a purpose is a special case of a warranty of merchantability in which the customer is purchasing a particular product for a particular purpose, and the manufacturer or retailer is aware of that purpose. Under such circumstances the product is being sold with the implied promise that it will meet the purchaser’s special needs.

The Lesson: If you have a problem with a defective product, don’t assume you are limited to the written warranty. If you can’t get the manufacturer or retailer to rectify the situation to your satisfaction, contact your state consumer protection agency or an attorney. If you are injured by a defective product you can use other legal theories to help in recovering damages. These theories include negligence and strict liability in tort.