n.the realm of works that are unprotected by copyright or other intellectual property rightsBehrnd-Klodt 2008, 223Work that has entered the public domain, with limited exceptions, generally may not again be protected by copyright, even if included in a new work. For example, if a public domain photograph is included in a new book, the new content may be protected by copyright, but not the photo.Hirtle 2012Once copyright in a work expires (or if it never had it in the first place), the work returns to its natural state as part of the public domain. When works rise into the public domain, anyone is free to use, reuse, remix, and build upon them.Dryden 2014, 73Another way to discern what institutions choose to digitize is to look at selection from the perspective of “copyright complications.” Broadly speaking, materials can be divided into three categories: materials in the public domain (i.e., the copyright has expired or never existed, as in U.S. federal government documents), materials in which the repository owns the copyright, and materials in which a third party owns the copyright.Hirtle 2015Some people will refer to things as being in the public domain when they can be accessed by the public. A public record in an office is in the public domain in this sense. But public domain in the copyright sense is different. Copyright public domain means that the work is not protected by copyright. This could be because of the lack of appropriate subject matter or through expiration of copyright.Duke Law 2020The public domain is the realm of material—ideas, images, sounds, discoveries, facts, texts—that is unprotected by intellectual property rights and free for all to use or build upon.
With regard to copyright, works in the public domain include those never protected by copyright, those released to the public domain by their creators, and those for which copyright has expired.