Detecting plagiarism

In many cases, instructors or TAs are able to identify plagiarism in course assignments based on poor citation methods or a lack of citations, off-topic papers, or based on their own disciplinary knowledge of the area of study. There are a number of other signs to look for when reviewing student assignments, including:

  • A common form of plagiarism manifests as incomplete paraphrasing or “tracing”, where a passage is copied from another source and a handful of words have been changed to synonyms but the structure and majority of text from the original passage remains intact.
  • Plagiarism also occurs when a student obtains an assignment from a friend and attempts to rewrite or “edit” the paper to reduce the amount of exact text matches. This is often detected by plagiarism detection software, or when similarities become evident during grading.
  • While sometimes more difficult to detect, purchased papers are often identified by the presence of:
      • Elevated language and quality of writing compared with a student’s previous work
      • Topic/sources are dated or do not reflect assignment



While grading any assignment, look for any of the following signals:

  • Changes in quality and level of writing within the paper
  • Strange syntax, e.g. an abundance of fragmented sentences and frequent typos
  • Strange structure, such as lack of formal introduction or conclusion, or repetitive paragraphs
  • Abrupt changes in font, style, and formatting
  • A feeling that some of the text is familiar to you
  • Mixed citation methods (e.g. parenthetical citations and footnotes in same paper)


Instructors may wish to use plagiarism detection software in their courses.

See also: