<P> In most countries the term of rights for patents is 20 years, after which the invention becomes part of the public domain . In the United States, the contents of patents are considered valid and enforceable for 20 years from the date of filing within the United States or 20 years from the earliest date of filing if under 35 USC 120, 121, or 365 (c). However, the text and any illustration within a patent, provided the illustrations are essentially line drawings and do not in any substantive way reflect the "personality" of the person drawing them, are not subject to copyright protection . This is separate from the patent rights just mentioned . </P> <P> A trademark registration may remain in force indefinitely, or expire without specific regard to its age . For a trademark registration to remain valid, the owner must continue to use it . In some circumstances, such as disuse, failure to assert trademark rights, or common usage by the public without regard for its intended use, it could become generic, and therefore part of the public domain . </P> <P> Because trademarks are registered with governments, some countries or trademark registries may recognize a mark, while others may have determined that it is generic and not allowable as a trademark in that registry . For example, the drug "acetylsalicylic acid" (2 - acetoxybenzoic acid) is better known as aspirin in the United States--a generic term . In Canada, however, "Aspirin", with an uppercase A, is still a trademark of the German company Bayer, while aspirin, with a lowercase "a", is not . Bayer lost the trademark in the United States, the UK and France after World War I, as part of the Treaty of Versailles . So many copycat products entered the marketplace during the war that it was deemed generic just three years later . </P> <P> Bayer also lost the trademark in the same jurisdictions for "Heroin" which it trademarked a year before it trademarked Aspirin . </P>

When do works fall into the public domain