We leave it to the instructors to look at a paper and the originality report to make the determination of whether or not something is plagiarism, and to what extent—intentional plagiarism, unintentional plagiarism, improper/lack of citation, or mere coincidence. Best practices from instructors suggest that Turnitin OriginalityCheck be used as a teaching tool to address citation and academic honesty, not only as a punitive tool.
There is also a helpful video for instructors on how to view the Similarity Report and goes over many of the OriginalityCheck features . There is a similar video tutorial for students on how to view their OriginalityCheck feedback as well.