What is Plagiarism in Research? Definition Types & Examples

Plagiarism in research is using someone else’s work without acknowledging the original author, and it’s treated as a form of academic theft with consequences that can derail careers. For students, it can mean suspension or expulsion; for researchers, it can destroy credibility and block future publication in scientific journals. Because the stakes are so high, the key is knowing what counts as plagiarism—not just what feels “wrong.”

Plagiarism is commonly grouped into three types: direct (or complete) plagiarism, accidental plagiarism, and self-plagiarism. Direct plagiarism is the most serious. It happens when a writer copies and pastes another person’s work in full and presents it as their own. The transcript frames this as deliberate cheating—often motivated by laziness—and warns that the fallout is typically severe.

Accidental plagiarism is less about intent and more about citation and presentation errors. It can occur when citations are missing or incorrect, or when quotation practices don’t match the level of copying. One example uses a statement from a paper by “Smith et al.” The authors cite the source at the end of the statement, but because they reproduce the exact wording without quotation marks, the text is still treated as plagiarism. The fix is to either (1) enclose the copied wording in quotation marks and cite it, or (2) introduce the quote with attribution such as “as Smith et al. state,” followed by the quoted text. The guidance also cautions against relying heavily on long, unaltered passages from other papers; exact quoting should be reserved for moments where precision is essential, such as a definition or a philosopher’s statement.

Even when writers paraphrase, citation still matters. The transcript stresses that paraphrasing the original text into new wording does not remove the obligation to cite the source, because the underlying idea or concept still belongs to someone else. Without a citation, paraphrased material can still be judged plagiarism.

Self-plagiarism is the third category and often surprises researchers. It involves reusing text (and even figures) from one’s own previously published work in a new paper without meeting the required permissions and transformations. The transcript explains that once a paper is published, copyright for the text typically belongs to the publisher, so reusing unaltered text is not allowed; paraphrasing is required. The same principle applies to figures: reusing them exactly requires permission from the original publisher, and if permission isn’t granted, the figure must be modified.

A related ethical breach is submitting the same paper to multiple journals at the same time. Journal submission agreements generally require that the work has not been published before and is not under consideration elsewhere. The recommended process is to submit to one journal, wait for the decision, and only then submit to another if the manuscript is rejected—repeating until the work is accepted.