What is Plagiarism?
What is plagiarism? In minor cases, it can be the quotation of a sentence or two, without quotation marks and without a citation (e.g., footnote) to the true author.
In the most serious cases, a significant fraction of the entire work was written by someone else: the plagiarist removes the true author(s) names(s) and substitutes the plagiarist's name, perhaps does some re-formatting of the text, then submits the work for credit (e.g., term paper or essay) or as part of the requirements for a degree (e.g., thesis or dissertation), or even as a professional/personal concern (e.g., article, blog entry, news item, etc.).