Defining The Public Domain

Definitions of the boundaries of the public domain in relation to copyright, or intellectual property more generally, regard the public domain as a negative space, that is, it consists of works that are no longer in copyright term or were never protected by copyright law. According to James Boyle this definition underlines common usage of the term public domain and equates the public domain to public property and works in copyright to private property. However, the usage of the term public domain can be more granular, including for example uses of works in copyright permitted by copyright exceptions.

Such a definition regards work in copyright as private property subject to fair use rights and limitation on ownership. A conceptual definition comes from Lange, who focused on what the public domain should be: "it should be a place of sanctuary for individual creative expression, a sanctuary conferring affirmative protection against the forces of private appropriation that threatened such expression". Patterson and Lindberg described the public domain not as a "territory", but rather as a concept: "There are certain materials - the air we breathe, sunlight, rain, space, life, creations, thoughts, feelings, ideas, words, numbers - not subject to private ownership. The materials that compose our cultural heritage must be free for all to use no less than matter necessary for biological survival."

The term public domain may also be interchangeably used with other imprecise and/or undefined terms such as the "public sphere" or "commons", including concepts such as "commons of the mind", the "intellectual commons", and the "information commons".