A Few Latin Abbreviations for References: ‘Ibid.’ and the ‘Id.’ Group
Latin abbreviations used to be much more common in scholarly references than they are today, but some still appear in citations and notes. Those which continue to be used relatively frequently in modern scholarship (‘et al.’ is a good example) tend to be clear to readers familiar with academic or scientific writing, but a few Latin abbreviations once common in references are now used so rarely and by so few scholarly publishers that correct patterns of usage and even their meanings have become clouded. Yet academics and scientists working in certain fields are nonetheless required to employ such abbreviations on occasion, and researchers and students still encounter them while consulting earlier sources. ‘Ibid.’ and the ‘id.’ group are abbreviations of this kind, and their meanings are very specific, so a little advice on using them correctly may prove helpful.

The abbreviation ‘ibid.’ is short for the Latin word ‘ibidem,’ which means ‘in the same place’ or ‘in that very place.’ It usually appears in roman font, but italic font is sometimes used or required, and it is occasionally shortened even further to ‘ib.’ The use of this abbreviation now tends to be restricted to footnote and endnote references, particularly in the humanities and almost exclusively when guidelines call for it rather than as an author choice. It is used instead of repeating bibliographical information when a source is cited again immediately (without any intervening references) after it has been cited in the preceding note or in the preceding sentence within a note. Because the abbreviation means ‘in that very place,’ it must be used with great care: only if everything about the second citation is exactly the same as the first can it be used alone, and any information that differs must be provided along with ‘ibid.’ (e.g., ‘ibid., p.8’ for referring to the same author and title but a different page). ‘Ibid.’ should only be used if the reference and other information intended are absolutely clear; if there is any potential for confusing the reader, it should be avoided. A comma sometimes (but not always) appears between ‘ibid.’ and a following page number or other indicator of location, so the relevant guidelines should always be consulted.

The abbreviation ‘id.’ is the shortened form of the Latin word ‘idem,’ which means ‘the same person.’ That is only the masculine form, however, so if the person referred to is feminine, the abbreviation should be ‘ead.’ for the Latin word ‘eadem.’ The plural forms are ‘eid.’ for the masculine ‘eidem’ and ‘eaed.’ for the feminine ‘eaedem,’ with the plural meaning being ‘the same people.’ The full versions of these words are often used instead of the abbreviations, but if space is limited or publisher guidelines specify abbreviated forms, the abbreviations are used in either roman or italic font. Whether the full words or the abbreviations are used, they serve as substitutes for author names when works by the same author(s) are cited consecutively. A comma should normally follow the abbreviation or Latin word, just as it would an author’s name. Keep in mind that either form (abbreviated or full) must be used appropriately in terms of gender and number, so the name of a single male author should be replaced with ‘id.’ or ‘idem,’ the name of a single female author with ‘ead.’ or ‘eadem,’ the names of joint male authors or a mixture of male and female authors with ‘eid.’ or ‘eidem,’ and the names of joint female authors with ‘eaed.’ or ‘eaedem.’ If there is any doubt about the author(s) intended or the gender of the author(s), the use of author names should be preferred.