Copyrights and patents are, at least in theory, granted for one-off fixed terms. On the other hand, trademarks are valid as long as the trademark owner actively defends and uses them.

However, the owner must maintain his or her trademark registration with their state's trademark registry. Often there will be a periodic renewal fee involved.

In the United States patents and copyrights eventually expire and become part of the public domain, but trademarks don't.

A trademark is a distinctive symbol, phrase, name, style, picture, or design that a business uses to identify its products and itself to the public. If the business offers a service instead of a product then the trademark is also known as a service mark.

Trademark law has been established to protect consumers from being deceived or confused about the quality and the origin off a product. The trademark owner does this by stopping his or her competitors from using their mark or a trademark that people are likely to confuse with theirs.

This could happen if, for example, another tissue manufacturer calls itself "Kleenex" or if the name is sufficiently similar. This would be the case, for example, if a beer company tries to imitate "Budweiser" and calls itself "Badweiser."

Trademarks are protected when the law permits trademark owners to prevent competitors from infringing on their marks by using marks that are confusingly similar. Although it isn't necessary to show that infringement was intentional, if it can be proven that there was the intent to deceive then the settlement for an infringement lawsuit can be greater.

Trademarks aren't strictly treated as property because some words have to remain free in order to describe or to identify a general class of products. Therefore, generic terms won't be protected. For example, you if you owned the trademark for "Apple" you couldn't use it as a trademark for the fruit.

The trademarks that can be most easily protected are those that use invented words, such as "Polaroid."

In addition, if a trademark identifies the source of services or goods, it can help the consumer to identify those goods and services which meet their expectations. Because trademarks fix responsibility they are an incentive for companies to maintain their good reputations and the quality of their products.

If quality is not consistent then it can lead to the mark being abandoned. If so the law won't continue to protect the trademark because it no longer functions as the indicator of that particular product.

Abandonment of a trademark can also happen by "naked licensing." This happens when the owner grants rights for someone else to use the mark but doesn't sufficiently control when or how they can use it. If that happens then the trademark would be released for general use.