Copyright is the legal right of ownership of a work that exists in a fixed, tangible form. It protects original works of authorship such as novels, essays, poetry and plays, artwork and architecture, computer software, and movies and sound recordings. Copyright gives the owner the exclusive right to reproduce, modify, adapt, distribute, and display the work, or grant others those rights. Ownership typically belongs to the creator, but in some cases it may belong to the creator's heirs, employer, or the publisher of the work. It's best to assume a work is protected until you are able to verify its status.

Expanded information can be found on the Copyright in General webpage of the U.S. Copyright Office.

Copyright applies to a limited term, and some works have never been copyrighted. When a work enters the public domain it is free from all copyright restrictions. You can do anything you want with public domain works, however, you must still cite the work.

The following are in the public domain:

• All works published before 1929;
• All US Government Documents (but not all STATE Government Documents);
• Works published between 1929 and 1963 with copyright notices, but the copyrights were not renewed (Stanford University's Copyright Renewal Database and the University of Pennsylvania's Catalog of Copyright Entries can help you find the status of books that fall within these years);
• Works published between 1929 and 1977 without copyright notices;
• Works published between 1978 and March 1, 1989 without copyright notices and without subsequent registration.

In addition, an author may voluntarily place a work into the Public Domain at any time. Detailed information on copyright term and conditions, compiled by Cornell University, can be found on their Copyright Information Center webpage.