Citation glossary
Plain-language definitions of the terms you'll meet when citing sources.
- Annotated bibliography
- A list of sources where each citation is followed by a short paragraph that summarizes or evaluates the source.
- APA style
- The citation and paper format of the American Psychological Association, now in its 7th edition. It uses author–date citations and a References list.
- Chicago style
- The style of The Chicago Manual of Style, now in its 18th edition (2024). It has two systems: notes and bibliography, and author-date.
- DOI (Digital Object Identifier)
- A permanent ID for a scholarly work, such as an article, book chapter or dataset, that keeps pointing to it even if its web address changes.
- et al.
- Latin for “and others.” Citation styles use it to shorten a list of authors, but each style starts using it at a different point.
- Harvard referencing
- A family of author–date citation styles. There's no single official version, so follow the guide your school uses.
- ibid.
- Short for the Latin ibidem, “in the same place.” In footnotes it means “the same source as the note just before.”
- IEEE style
- The numbered citation style of the Institute of Electrical and Electronics Engineers, used in engineering and computing.
- In-text citation
- A short pointer in your sentence to the full entry for a source in your reference list.
- ISBN (International Standard Book Number)
- A product number for a book. Each edition and format (hardback, paperback, e-book) has its own ISBN.
- MLA style
- The Modern Language Association's style for the humanities, now in its 9th edition (2021). It uses author–page citations and a Works Cited list.
- PMID (PubMed ID)
- The unique number of a record in PubMed, the database of biomedical and life-sciences literature. It isn't the same as a PMCID.
- Preprint
- A version of a paper shared publicly, often before peer review. Results may change before publication.
- Reference list vs. bibliography vs. works cited
- Three names for the list of sources at the end of a paper. Which one you use depends on the citation style.
- Retraction
- The formal withdrawal of a published paper by its journal because its findings can't be relied on, for example because of serious errors or misconduct.
Need step-by-step help? See the citation guides.