ibid.

Short for the Latin ibidem, “in the same place.” In footnotes it means “the same source as the note just before.”

You’ll mostly see “ibid.” in Chicago’s notes and bibliography system.

1. Mara Quillfeather, Tides of Invention (Harbor Lane Press, 2023), 45.
2. Ibid., 48.

The 18th edition of the Chicago Manual discourages “ibid.” and prefers a short note instead (author, short title, page), because readers would otherwise have to look back to find the source. Ibid. is still allowed when it refers to the note immediately before.

APA and MLA don’t use “ibid.” at all.