Plagiarism is basically the copying of another person's work, ideas, words or phrases as your own. Plagiarism has been around for many centuries, but with advancements in technology, it has become a more serious issue today. In academic contexts, there are different definitions of plagiarism according to the school. For the most part, a professor may accuse a student of plagiarizing if they use someone else's work in a "derived work" (a book, song, poem etc.) and the professor does not have exclusive rights to the work.
On the academic side of things, plagiarism can fall into several categories, including: Indirect plagiarism, Conveyor plagiarism, and Internal or Electronic Plagiarism. Indirect plagiarism is when a phrase or sentence is written by someone who has borrowed it from someone else. For instance, if you read Shakespeare's Sonnets and compare them to a modern work of fiction, chances are you will find that the phrases used have been taken directly from the source. Conveyor plagiarism is when the same work is copied from a source via words, phrases, or passages without the original writer's permission. Internal or Electronic Plagiarism occurs when an academic paper is submitted electronically and the author does not have the proper permissions to post the paper online for viewing by others.
With the use of quotations, Plagiarism can be a difficult issue. The best way to avoid plagiarism in academic writing is to first consult with a professor about your use of quotations in order to determine if they are appropriate and if you need any type of permits to use them. If you do not get a professor to give you the okay, you can still avoid plagiarism by looking for quotes that closely resemble another source and reading the passage out of context. If you feel that you may be plagiarizing you should consult a professor as to the exact steps you need to take.