Idem and Ibid

By Maeve Maddox

A reader asks,

Could you discuss the use of “id.” in conjunction with referencing citations, especially web links?

The abbreviation id. in bibliographical citations stands for Latin idem: “the same.”

The abbreviation id. and the word idem are often seen in older scholarly works, but modern style guides, like The Chicago Manual of Style, no longer countenance the use:

14.30 “Idem”
When several works by the same person are cited successively in the same note, idem (“the same,” sometimes abbreviated to id.) has sometimes been used in place of the author’s name. Except in legal references, where the abbreviation id. is used in place of ibid., the term is rarely used nowadays. Chicago discourages the use of idem, recommending instead that the author’s last name be repeated.

Ibid. is another abbreviation related to the Latin word for same. It stands for ibidem, “in the same place” and usually refers to a single work cited in the note immediately preceding. Here is an example from the bibliographical endnotes for Chapter I, “Maid of France” in Marina Warner’s Joan of Arc: The Image of Female Heroism:

18. Pernoud, Retrial, pp. 197-8. (first mention of the book cited)
19. Ibid, p. 201.
20. Ibid, p. 134.
21. Ibid, p. 75.
22. Ibid, p. 177.
23. Ibid, p. 149.
24. Ibid, p. 96.
19. Ibid, pp. 90-2.

All the references marked Ibid. are from the same source.

Note: “Pernoud, Retrial” is the abbreviated form that Warner uses in the notes for Regine Pernoud’s The Retrial of Joan of Arc: The Evidence at the Trial for Her Rehabilitation.

Ibid, italicized when referred to as a word, is not italicized in use. Ibid is pronounced with short i in both syllables. The i in idem is also a short vowel, as is the e.

The reader asks about the use of id. in reference to Web links. I can’t recall having come across it, but if people do use it online, the same conventions that are described here would apply. For example:

Maddox, Maeve. “Let the Word Do the Work.” Daily Writing Tips. May 30, 2007. Web. August 13, 2015.


The pattern for a Web citation (MLA style) is as follows:

Last name, First name. “Article Title.” Website Title. Publisher. Date Month Year Published. Web. Date Month Year Accessed.

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2 Responses to “Idem and Ibid”

  • thebluebird11

    Maeve, thank you for this little post, especially the bit at the end regarding the format for citing online sources of information. I would never have even thought to mention the date accessed.
    Also, thank you for including the pronunciation of the Latin words; I am not familiar with pronunciation except for the most common words.

  • Roberta B.

    “Web,” only? No website/internet address or domain name needed?

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