‘ibid.’ vs. ‘id.’: Understanding Citation Abbreviations in Research

Introduction

When writing academic papers, particularly in humanities, law, and historical research, proper citation formatting is essential to ensure clarity, credibility, and proper attribution of sources. Two commonly used abbreviations in citation formatting are ‘ibid.’ and ‘id.’.

Both ‘ibid.’ (short for ibidem, meaning “in the same place”) and ‘id.’ (short for idem, meaning “the same author”) help writers streamline citations by avoiding redundant references to the same source. However, their usage varies depending on citation style, field of study, and journal requirements.

This article explores the meaning, usage, formatting, and best practices for using ‘ibid.’ and ‘id.’ in academic writing, with examples from major citation styles such as Chicago, Bluebook, and Oxford referencing.

1. Understanding ‘ibid.’ in Academic Citations

1.1. What Does ‘ibid.’ Mean?

‘Ibid.’ is the abbreviation for the Latin term ibidem, which translates to “in the same place.” It is used to refer to the same source as the immediately preceding citation.

Using ‘ibid.’ avoids unnecessary repetition when citing the same source consecutively, saving space and improving readability.

1.2. When to Use ‘ibid.’

• When referencing the same source as the previous footnote or endnote.
• When citing the same page number as the previous reference, ‘ibid.’ is used alone.
• When citing a different page number from the previous reference, ‘ibid.’ is followed by a page number.

1.3. Examples of ‘ibid.’ in Use

A. When the Citation is Exactly the Same as the Previous One

1. John Smith, History of Ancient Rome (Oxford University Press, 2010), 45.
2. Ibid.

B. When the Citation is From the Same Source but a Different Page

1. John Smith, History of Ancient Rome (Oxford University Press, 2010), 45.
2. Ibid., 50.

In this case, the second citation refers to page 50 of the same book cited in footnote 1.

1.4. Citation Styles That Use ‘ibid.’

‘Ibid.’ is commonly used in:

• Chicago Style (Notes and Bibliography)
• Oxford Referencing (Footnotes and Endnotes)
• Turabian Style (A variation of Chicago Style for students)

1.5. When Not to Use ‘ibid.’

• When the citation is NOT consecutive (i.e., when another source appears between references).
• In APA and MLA styles, which use author-date citation formats instead.
• Some journals prefer shortened citations over ‘ibid.’ due to readability concerns.

2. Understanding ‘id.’ in Academic Citations

2.1. What Does ‘id.’ Mean?

‘Id.’ is the abbreviation for the Latin term idem, meaning “the same author.” It is commonly used in legal writing and refers to the same author as the previous citation but may reference a different work by the same author.

Unlike ‘ibid.’, which refers to the same source, ‘id.’ specifically refers to the same author but can be used when citing multiple works by that author.

2.2. When to Use ‘id.’

• When citing the same author as the previous reference, but the source or page number may differ.
• Used mainly in legal citations (Bluebook style).

2.3. Examples of ‘id.’ in Use

A. When Referring to the Same Author and Source

1. John Doe, Constitutional Law Principles, 2nd ed. (Harvard Law Review, 2021), 125.
2. Id., 130.

This example shows that footnote 2 refers to the same author and book but a different page.

B. When Referring to the Same Author but a Different Work

1. John Doe, Constitutional Law Principles, 2nd ed. (Harvard Law Review, 2021), 125.
2. Id., Federalism in America (Yale University Press, 2019), 90.

Here, ‘id.’ means that John Doe is the same author, but now a different book is being referenced.

2.4. Citation Styles That Use ‘id.’

• Bluebook (Legal Citations)
• Oxford Referencing (Legal Documents)
• Some Chicago Style Applications in Legal Writing

2.5. When Not to Use ‘id.’

• If the author is different from the previous reference.
• In academic papers outside of legal studies, where standard author-date referencing is preferred.

3. Differences Between ‘ibid.’ and ‘id.’

4. Best Practices for Using ‘ibid.’ and ‘id.’ in Academic Writing

4.1. Follow Journal or Institutional Guidelines

• Always check whether your journal, university, or discipline prefers ‘ibid.’, ‘id.’, or short-form citations.

4.2. Avoid Overusing ‘ibid.’ or ‘id.’ for Readability

• If a document contains many consecutive citations, some journals prefer shortened author-title references instead of ‘ibid.’.

4.3. Be Consistent with Formatting

• Ensure that punctuation, italics, and capitalization are formatted correctly.

4.4. Double-Check for Ambiguity

• If another source is cited in between, do not use ‘ibid.’ or ‘id.’ to avoid confusion.

5. Alternative Citation Styles That Do Not Use ‘ibid.’ or ‘id.’

Certain referencing styles prefer shortened citations instead of Latin abbreviations:

• APA Style: Uses author-date in-text citations (e.g., Smith, 2019, p. 45).
• MLA Style: Uses author-title citations instead of ‘ibid.’ (e.g., Smith, History of Rome, p. 45).
• Harvard Referencing: Uses author-date citation but allows shortened references for repeat citations.

If your journal or professor discourages ‘ibid.’ or ‘id.’, opt for shortened author-title citations instead.

Conclusion

Using ‘ibid.’ and ‘id.’ correctly enhances citation clarity, improves readability, and streamlines reference formatting in academic writing. While ‘ibid.’ is used to reference the same source as the previous citation, ‘id.’ refers to the same author, often used in legal citations.

By following journal-specific guidelines, ensuring consistency, and avoiding overuse, researchers can apply these abbreviations effectively and maintain professional academic writing standards.

If unsure, always consult your journal’s submission guidelines or use alternative citation methods to maintain clarity.