A brand consists of a single insight or idea in the customer’s mind, wedded to a sign—a name and symbol—that serves as a convenient shorthand for that idea.

Trouble may arise if two or more ideas (products or services) share the same name or symbol. Apple Computer was sued in the early 1980s for using the same name as the Beatles’ record company. The suit ended with an agreement that the computer firm would stay out of the music business.

This is a common sort of arrangement. There is no problem with the same name (or a similar logo) being used by companies that operate in completely different categories or geographic areas: customers are not likely to be confused. However, disagreements can arise when the boundaries blur, as when Apple started selling songs through its online iTunes service, or when the American Budweiser beer tried to move into European markets claimed by the Czech Budweiser, resulting in protracted legal disputes.

A strong brand is the most powerful means for fending off competitors when other tactics such as copyright protection or exclusive distribution are exhausted. When LEGO invented its interlocking plastic bricks in the 1940s, it was able to patent them. But patents eventually expire. LEGO now fends off makers such as Mega Bloks and others by virtue of having a stronger brand, using a combination of design, innovation, quality, and brand experience to maintain the loyalty and passion of its customers.

Trouble of another sort crops up when a name that has long been associated with one company’s product becomes a generic term for a whole class of goods. English is littered with words that used to be trademarks: linoleum, cornflakes, aspirin, and dozens more. This happens in other languages too: in Italian, a bus is often called a pulman after the old coach maker, Pullman; in Czech, a razor blade is referred to as a ziletka, a Slavicized version of the name Gillette. When a name is judged to have become generic, its former owners lose the protection of trademark, since language belongs to everybody and no one can lay claim to a particular word.

This is a cruel irony of successful branding. On the one hand, you want customers to have your name on the tip of their tongue when they articulate a desire for your type of product. On the other hand, the name must be associated not so much with the thing itself (or the product category) as with the quality that transcends it—the insight that raises your product above the other commodity products in the same category.

Some trademarks are still acknowledged as belonging to one company, but are so widely used that their owners must be constantly vigilant, lest the names become generic. That’s why brands like Kleenex and Band-Aid add the word “brand” in tiny letters under the name on their packaging.

“Let me Xerox that for you.” “Please FedEx that to me.” “Go ahead and Google it.” Each of these actions might just as easily be fulfilled using the services of Canon, DHL, or Yahoo!, respectively. The challenge for brands that risk becoming verbs is not to occupy the number one position in customers’ minds—they have achieved that—but to keep customers mindful of why the brand means more than the product. They must achieve a higher insight that transcends product and stands for something more universally appealing. To survive into the future, Xerox needs to be more than just “number one in copiers,” FedEx needs to be more than just “overnight,” and Google needs to be more than just “search and find.”