The Oxford English Dictionary (OED) Online defines plagiarism as "the action or practice of taking someone else's work, idea, etc., and passing it off as one's own; literary theft." It is plagiarism when you buy or use a term paper someone else wrote; cut and paste parts of an online book or article without citing the source; use, or even paraphrase another author's words or ideas without citing him or her. Whether it is done deliberately or accidentally, it is plagiarism.
You must give credit whenever you use: