Under U.S. law, any expression of an original idea is considered intellectual property and is protected by copyright law. This includes books, print or online articles, movies, TV shows, music and song lyrics or any other form of expression that is recorded in some way. A person commits plagiarism when he steals someone else's ideas and passes them off as his own or when he borrows those ideas without giving credit to the source.
Thanks to the Internet, intentional plagiarism has become commonplace. A plethora of websites exist to sell term papers and essays to students or to match students with "ghostwriters" who do the work for them. The computer age also makes it easy to copy and paste entire blocks of text from a variety of websites, thus creating the appearance of an "original" paper. Students commit intentional plagiarism for a variety of reasons, including because "everybody else is doing it," because they feel pressured to get a good grade or they wanted to see if they could get away with it.
Not everyone who plagiarizes does so intentionally, however. Many people are simply confused as to what constitutes plagiarism, especially students who may have never written a paper before. Basically, any information that is not common knowledge or is not the writer's own idea need to be credited. The way sources are credited varies depending on the type of paper being written and the writing style used. Most high school and college research papers are written in either MLA or APA styles, which stand for Modern Language Association and American Psychological Association, respectively. Both styles have their own rules for citing sources in text, and students should be aware of these citation rules before beginning work on their paper.
Fortunately, there are a variety of techniques writers can use to ensure they don't inadvertently steal someone else's ideas. When using Internet sources, never copy and paste text without using quotation marks and attributing the source. You can rewrite the information in your own words, but you still need an attribution. Also, rearranging or changing a few words in someone else's sentence is still plagiarizing. When editing or rewriting, take care not to change the meaning of a sentence or cut out the attribution. Saving multiple drafts of your work can help you avoid errors of this type. It also may be helpful to run your work through an online plagiarism detector before turning it in. Many websites provide this service for free or for a minimal fee.