There are some notable exceptions. What about press releases for example? Such and such a company or entity issues a statement about a new product, upgrade or whatever. Isn't the company expecting people to copy the notice? Yes, pretty obviously. In fact, they would probably like to have the entire press release reproduced and not just abstracted or excerpted. But that is far from the common situation.
You cannot copyright facts. If I read that the temperature in Phoenix is 110 degrees, that is a fact and not covered by copyright. Be careful in how you reproduce those fact however, the wording of the original is copyrighted.
Another exception is fair use. The Wikipedia definition is pretty good, here it is:
Fair use is a limitation and exception to the exclusive right granted by copyright law to the author of a creative work. In United States copyright law, fair use is a doctrine that permits limited use of copyrighted material without acquiring permission from the rights holders. Examples of fair use include commentary, criticism, news reporting, research, teaching, library archiving and scholarship. It provides for the legal, unlicensed citation or incorporation of copyrighted material in another author's work under a four-factor balancing test.While I am at it, Wikipedia is governed by the Creative Commons, another exception to the Copyright Law. This particular quote is covered by the Creative Commons Attribution-ShareAlike License License.
Another exception is the use of United States Federal Government documents. Not State documents, not county etc. but only US Government documents. However, there may be copyrighted material in a government document and you need to read carefully to see if any rights have been reserved.
Now back to fair use. There is a balancing criteria. Here is the quote from 17 United States Code Section 107:
Notwithstanding the provisions of sections 17 U.S.C. § 106 and 17 U.S.C. § 106A, the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include:Got it? If not, you are not alone. Unfortunately, most of the law is vague and difficult to understand. The simple answer, always attribute any copy. The second part, never copy an entire work even if the work is only one paragraph or one sentence long. Rewrite in your own words.
The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors
- the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
- the nature of the copyrighted work;
- the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
- the effect of the use upon the potential market for or value of the copyrighted work.
Last, you can always ask permission to reproduce a work.