In academic-type works, you may have frequently seen citations to a mysterious ‘Ibid.’ and wondered who it was. It is not an ancient Greek philosopher, but rather a handy referencing tool. ‘Ibid.,’ when found in references or footnotes, is referencing a source that was cited in the preceding footnote or endnote. Essentially, it means “same as previous source.” If something references Ibid., you must look at the note that came before it to find the source.
For example:
Endnote:
[1] J. Smith, How to Reference Your Sources (New York: Academic, 2016), p. 102.
[2] Ibid.
[3] Ibid. p. 151.
In the example, the second endnote referenced the same source and same page as endnote [1]. The third endnote references the same source but a different page.
Ibid. is short for the Latin word ibidem, which means “in the same place.” Since it is an abbreviation, a period (or full-stop) must always be placed at the end of the word. Since it is a foreign word, Ibid. is traditionally used in italics, though some styles, such as ‘Harvard,’ do not require italics.
In the ‘Harvard’ referencing style, Ibid. can also be used for references within the text. However, it should only be used if there is a close by and obviously visible citation from the same source. Some writing styles, such as APA, forgo the use of Ibid. all together in favor of the author-date format to reference repeated source.
Sources:
http://www.dictionary.com/browse/ibid?r=67
http://www.chicagomanualofstyle.org/qanda/data/faq/topics/Documentation/faq0242.html
http://www.hup.harvard.edu/resources/authors/pdf/hup-author-guidelines-notes.pdf
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