“Ibid.”

The abbreviation ibid. (from ibidem, “in the same place”) usually refers to a single work cited in the note immediately preceding. It must never be used if the preceding note contains more than one citation. It takes the place of the name(s) of the author(s) or editor(s), the title of the work, and as much of the succeeding material as is identical. If the entire reference, including page numbers or other particulars, is identical, the word ibid. alone is used (as in note 7 below). The word ibid. (italicized in this paragraph only because it is a word used as a wordsee 7.58) is capitalized at the beginning of a note and followed by a period. To avoid a succession of ibid. notes, the content of notes 6–8, 10, and 11 below might instead be placed parenthetically in the text in place of the note references (see 13.64).

5. Farmwinkle, Humor of the Midwest, 241.
6. Ibid., 258–59.
7. Ibid.
8. Ibid., 333–34.
9. Losh, Diaries and Correspondence, 1:150.
10. Ibid., 2:35–36.
11. Ibid., 2:37–40.

Ibid. may also be used within one note in successive references to the same work.

8. Morris Birkbeck, “The Illinois Prairies and Settlers,” in Prairie State: Impressions of Illinois, 1673–1967, by Travelers and Other Observers, ed. Paul M. Angle (Chicago: University of Chicago Press, 1968), 62. “The soil of the Big-prairie, which is of no great extent notwithstanding its name, is a rich, cool sand; that is to say, one of the most desirable description” (ibid., 63).


“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.