Turnitin is a suite of plagiarism detection and grading tools. It checks student assignments against internet sources and a database of student papers to generate originality reports, which indicate what percentage of a submission matches existing sources and shows where in the text the matches occur. While a high similarity score may indicate plagiarism, it does not always, and Turnitin has some limitations in terms of the sources it can check against. Consistent policies are needed for reviewing originality reports and communicating expectations to students.