Here is Western Michigan University's current definition of plagiarism, adopted in 2016.

"Plagiarism is the use of someone else’s language, ideas, or other material without making the source(s) evident in situations where there is a legitimate expectation of original work.  Plagiarism does not occur when efforts to promptly identify sources by making source use apparent to the audience of the submitted material are obvious.  Plagiarism may not necessarily include mistakes in citation style.

A legitimate expectation of original work exists for numerous circumstances, including (but not limited to): scholarly writing, technical presentations and papers, conference presentations and papers, online discussion postings, grant proposals, patents, book and other manuscripts, theses and dissertations, class assignments, artistic works, computer code, algorithms, and other creative works.

This definition applies to the entire WMU community, which includes all faculty; students; staff; visiting faculty, scholars, administrators; and any other person governed by academic research and other policies of the University."

Graduate Students and Source Text Use Runtime: 06:34 min
What does the literature tell us about graduate students and the issues they face writing theses and dissertations and working with sources?

Non-native Speakers and Source Text Use Runtime: 02:30 min
A number of published research studies in the fields of writing composition and second-language instruction that seem to indicate that non-native English speakers, that is students and researchers for whom English is a second language, may have more issues with plagiarism than native English speakers.