What is "in the public domain"

Domain \Do*main"\, n. [F. domaine, OF. demaine, L. dominium, property, right of ownership, fr. dominus master, owner. See Dame, and cf Demesne, Dungeon.]

1. Dominion; empire; authority.

2. The territory over which dominion or authority is exerted; the possessions of a sovereign or commonwealth, or the like. Also used figuratively. [WordNet sense 2]

   The domain of authentic history.
   --E. Everett.

   The domain over which the poetic spirit ranges.
   --J. C. Shairp.

3. Landed property; estate; especially, the land about the mansion house of a lord, and in his immediate occupancy; demesne. [WordNet sense 2]
   --Shenstone.

4. (Law) Ownership of land; an estate or patrimony which one has in his own right; absolute proprietorship; paramount or sovereign ownership.

5. (Math.) the set of values which the independent variable of a function may take. Contrasted to range, which is the set of values taken by the dependent variable.

6. (Math.) a connected set of points, also called a region.

7. (Physics) a region within a ferromagnetic material, composed of a number of atoms whose magnetic poles are pointed in the same direction, and which may move together in a coordinated manner when disturbed, as by heating. The direction of polarity of adjacent domains may be different, but may be aligned by a strong external magnetic field.

8. (Computers) an address within the internet computer network, which may be a single computer, a network of computers, or one of a number of accounts on a multiuser computer. The domain specifies the location (host computer) to which communications on the internet are directed. Each domain has a corresponding 32-bit number usually represented by four numbers separated by periods, as 128.32.282.56. Each domain may also have an alphabetical name, usually composed of a name plus an extension separated by a period, as worldsoul.org; the alphabetical name is referred to as a domain name.

9. (Immunology) the three-dimensional structure within an immunoglobulin which is formed by one of the homology regions of a heavy or light chain.
   --Dict. Sci. Tech.

10. the field of knowledge, expertise, or interest of a person; as, he had a limited domain of discourse; I can't comment on that, it's outside my domain. [WordNet sense 5]

    Syn: domain, realm, field, area. [PJC]

11. a particular environment or walk of life. [WordNet sense 1]

    Syn: sphere, domain, area, orbit, field, arena. [PJC]

12. people in general; especially a distinctive group of people with some shared interest. [WordNet sense 4] Syn: world, domain. [PJC] Public domain,

    1. the territory belonging to a State or to the general government; public lands. [U.S.]

    2. the situation or status of intellectual property which is not protected by copyright, patent or other restriction on use. Anything

       in the public domain may be used by anyone without restriction. The effective term of force of copyrights and patents are limited by statute, and after the term expires, the writings and inventions thus protected go into the public domain and are free for use by all.

       Right of eminent domain, that superior dominion of the sovereign power over all the property within the state, including that previously granted by itself, which authorizes it to appropriate any part thereof to a necessary public use, reasonable compensation being made.