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|Intellectual property law|
Works are in the public domain if the intellectual property rights have expired, if the intellectual property rights are forfeited, or if they are not covered or protected by intellectual property laws. Examples include the English language, the formulae of Newtonian physics, the works of Shakespeare and Beethoven, and the patents on powered flight. The term is not normally applied to situations when the creator of a work retains residual rights in the work, in which case the use of the work is referred to as "under license" or with permission.
In a general context, public domain may refer to ideas, information, and works that are "publicly available", but in the context of intellectual property law (which includes copyright, patents, and trademarks), public domain refers to works, ideas, and information which are intangible to private ownership and/or which are available for use by members of the public.
As intellectual property rights are country-based, and laws vary to some extent, a work may be subject to such rights in one country but be in the public domain in another. Some rights, such as patents and trademarks, depend on registrations in each country in which rights are to be asserted, and in the absence of registration in any country, the work is not protected in that country.
History of public domain
Public domain did not come to fruition as a term until the mid-17th century, although as a concept “it can be traced back to the ancient Roman Law, as a preset system included in the property right system.”  The Romans had a large proprietary rights system where they defined “many things that cannot be privately owned” as res communes, res publicae and res universitatis. The term res commune was defined as “things that could be commonly enjoyed by mankind, such as air, sunlight and ocean.”  The term res publicae referred to things that were shared by all citizens, and the term res universitatis meant things that were owned by the municipalities of Rome.  When looking at public domain from a historical perspective, one could say the construction of the idea of "public domain" sprouted from the concepts of res commune, res publicae, and res universitatis in early Roman Law. 
When the first early copyright law was first established in Britain with the Statute of Anne in 1710, public domain did not appear. However, similar concepts were developed by British and French jurists in the eighteenth century. Instead of” public domain” they used terms such as publici juris or propriété publique to describe works that were not covered by copyright law.  The phrase "fall in the public domain" can be traced to mid-nineteenth century France to describe the end of copyright term. The French poet Alfred de Vigny equated the expiration of copyright with a work falling "into the sink hole of the public domain" and if the public domain receives any attention from intellectual property lawyers it is still treated as little more than that which is left when intellectual property rights, such as copyright,patents, and trademarks, expire or are abandoned. In this historical context Paul Torremans describes copyright as a "little coral reef of private right jutting up from the ocean of the public domain." Because copyright law is different from country to country, Pamela Samuelson has described the public domain as being "different sizes at different times in different countries".