Students should always be careful to avoid plagiarism when writing term papers and essays. There are severe academic consequences for students caught plagiarizing even a portion of their term paper - most will automatically receive a failing grade, and in many cases the student will be expelled from school entirely.
The reason why plagiarism is treated so seriously by teachers, professors, and school administrators is that plagiarism is considered a form of cheating. By copying another person's words or ideas without citing the source, not only are you failing to give proper credit to the author, but you are passing the work off as your own. You falsely represent to the reader of your essay (ex. your professor) that you came up with the words and ideas by yourself. This is no different than copying an exam answer off a classmate and pretending that you arrived at the answer yourself.
Actively remembering to cite your sources of information and recognizing the consequences for not doing so will help prevent deliberate cases of plagiarism. However, even well-intentioned students can get in trouble by failing to understand what constitutes as plagiarism and what does not.
The biggest misconception about plagiarism is that you only need to cite a source when you've directly copied the words of that source - for example if you copied a sentence word-for-word from a book into your term paper. These students mistakenly think that if you change the words of the sentence or put the author's ideas in your own words, it is not necessary to cite the source. This is not true!
Students must provide a citation whenever information from another source is used in their essay, even if the original words were changed. Plagiarism counts not only when you borrow other people's words, but also when you borrow their thoughts or ideas. Therefore, paraphrasing is not a substitute for citation. Neither is summarizing. The only time you can use information without attribution or credit is when the information is considered common knowledge - something that is generally accepted as a fact or can be easily found in reference materials.
Here are some other myths about plagiarism:
Plagiarism only counts if most of the research paper was plagiarized. FALSE: Even if only one phrase or sentence in the essay was copied without attribution, it is still considered plagiarism. It is easy to get away with plagiarism because it is so hard to detect and prove.