Distinctive design, graphics, logo, symbols, words, or any combination thereof that uniquely identifies a firm and/or its goods or services, guarantees the item's genuineness, and gives it owner the legal rights to prevent the trademark's unauthorized use. A trademark must be (1) distinctive instead of descriptive, (2) affixed to the item sold, and (3) registered with the appropriate authority to obtain legal ownership and protection rights. Trademark rights are granted usually for 7 to 20 years and, unlike in case of patents, are renewable indefinitely. These rights are protected worldwide by international intellectual property treaties and may be assigned by their owner to other parties. Although a trademark has no limited term of existence, the rights to use it may be lost due to misuse or lack of use. Trademarks are divided into 42 international classes, each class representing similar goods or services. Whereas a trademark may be registered under multiple classes, it is protected only in the class(es) relevant to the business or trade area of the item. And, whereas the use of symbol 'TM' does not provide any legal benefit, it precludes the infringer's defense of lack of knowledge of a trademark claim. Costs incurred in design and registration of, and in defending, a trademark are usually amortized over the life the trademark or 40 years, whichever is shorter. In balance sheets, trademarks are identified as intangible assets and, in some cases such as Coca Cola Co., are far more valuable than the firm's all other assets. The term trademark includes the associated term service mark (SM).