Ibid is a contraction of ibidem, a Latin word meaning “the same place.” This term is most commonly used for footnoting in scholarly texts, allowing the author to say “ibid” instead of citing a lengthy title. In legal texts, people may use “id,” a shortening of “idem,” a word which means “as mentioned previously.” If you've ever been reading a text and wondering about the identity of this “ibid” person who seems to get cited all the time, now you know!

Essentially, “ibid” is a fancy form of ditto marks. If, for example, you are referencing something like The Effects of Factory-Produced Emissions on the Greater Nile Watershed: An Environmental Study, that's a long title to have to refer to again and again. Instead, you can reference the title in a footnote, and then use “ibid” in future footnotes. If you move to a new location in the text, you can alert your readers with “Ibid (page 23)” or “Ibid, 23,” depending on what kind of citation format you are using.

When a new source is introduced, the “ibid” process begins all over again. In other words, if you cite The Effects of Factory-Produced Emissions on the Greater Nile Watershed: An Environmental Study once and follow with four additional citations marked with “ibid” before moving on to Cultural Practices in the Southern Nile Floodplain, an “ibid” after this source would refer to Cultural Practices in the Southern Nile Floodplain, not to the original text.

The use of “ibid” refers to both an author and a text. In some scholarly texts, people use “idem” to refer to an author alone if multiple works by the same author are being cited, as in “John Smith, Purple Elephants After Midnight (Saint Louis, University of Missouri Press, 1974), 367; idem, Under the Lily Trees (New York, St. Martin's Press, 1981), 284.” While replacing an author's name with “idem” might seem a bit lazy, some authors do have rather lengthy names and titles, and “idem” saves space and time.

Different scholarly disciplines have different rules about citations, and specific instructors, universities, and publications may have their own preference. For this reason, it is a good idea to consult a style manual before submitting material for publication, grading, or evaluation, to ensure that it meets the basic stylistic standards for the venue to which is it being submitted. While making small adjustments to footnoting practices may seem nitpicky to some, it ensures that material is standardized, and materials which have not been properly edited may be rejected.