According to the United States Copyright Office, "Copyright is a form of protection provided by the laws of the United States to the authors of 'original works of authorship.' " There are several classes of material, however, which are not protected by copyright.

Features

Under U.S. law, copyright is secured automatically once a work is created. Protections generally cover material of a literary, dramatic, musical, architectural or graphic work. Sound recordings are also protected.

Unfixed Material

When a work is not available in any tangible form, it falls under the category of unfixed material. This type of work, which includes unrecorded concerts or impromptu speeches, is not protected under U.S. copyright law.

Types

Titles, names, short phrases, familiar symbols, and listings of ingredients are excluded from copyright protection. Brand names and slogans associated with products or services, however, may fall under the protective umbrella.

Ideas and Common Property

Ideas, discoveries, or methods of operation are considered common property and therefore are not protected; only the expressions of such ideas can be copyrighted. The ideas and discoveries themselves are instead potentially eligible for a patent, which is much more difficult to obtain than a copyright.

Public Domain

Once a copyright expires, which occurs between 70 and 95 years after the author's death, the material falls into the public domain. At this point it can no longer be copyrighted.

Source:

U.S. Copyright Office: Copyright Basics

Bitlaw.com: Works Unprotected by Copyright Law

Resource:

ppdoc.com: What is Not Protected by Copyright?