Public domain is a legal category that covers government-owned land as well as creative works that the public may use freely. The creative works that may fall in the public domain include any scientific, artistic, or literary creation or invention. Such works are also called intellectual property. This article focuses on intellectual property that is in the public domain. For more information on public-domain land, see Public lands .
When intellectual property falls in the public domain, anyone can use, make, or sell it without paying royalties or becoming liable in a lawsuit. Creative works owned exclusively by a person or company are called proprietary material. The law can be used to prevent the theft or copying of such material. Laws governing intellectual property are, by treaty, similar in almost all countries.
All intellectual property begins as _proprietary material—_that is, material owned exclusively by an individual or a company. Different types of intellectual property enter the public domain in different ways. The three main categories of intellectual property are (1) chemical, mechanical, or electrical inventions, (2) material that can be copyrighted, including writings, computer programs, photographs, artwork, music, and motion pictures, and (3) trademarks, which are words or other symbols used as brand names.
A chemical, mechanical, or electrical invention enters the public domain if it is sold or publicized and no patent application is filed within a year. If patented, the invention passes into the public domain when the patent expires, usually 20 years from the date the patent application was filed. If the invention is a trade secret, the law allows the owner to keep it a secret unless the invention is patented or someone else independently discovers it.
Copyrighted material enters the public domain when the copyright expires. In the United States, the copyright remains in force for the author’s lifetime plus 70 years, or 95 years from publication if the author was hired by someone else to produce the work. In other countries, the copyright expires 20 years sooner in either case.
A trademark enters the public domain only if its use is permanently discontinued or if the trademark becomes widely used as a generic term. Countries other than the United States require that a trademark be registered before it can be enforced.
