Citation Signals

In law, a Citation or introductory signal is a set of phrases or words used to clarify the authority (or significance) of a legal citations it relates to a proposition. It is used in citations to present authorities and indicate how those authorities relate to propositions in statements. Legal writers use citation signals to tell readers how the citations support (or do not support) their propositions.

Most citation signals are placed in front of the citation to which they apply. Some of these citation signals include the following:

1. Idem

idem is a Latin term meaning "the same". It is commonly abbreviated as id., which is particularly used in legal citations to denote the previously cited source (compare ibid.). It is also used in academic citations to replace the name of a repeated author.

2. Ibid/bid

ibid. is an abbreviation for the Latin word ibidem, meaning "in the same place", commonly used in an endnote, footnote, bibliography citation, or scholarly reference to refer to the source cited in the preceding note or list item. This is similar to idem, literally meaning "the same", abbreviated Id., which is commonly used in legal citation. The previous reference should be immediately visible, e.g. within the same paragraph or page.

3. Loc. Cit.

Loc. cit is short for the Latin term Loco citato, which means “in the place cited”. It is used to repeat the title and page number for a given work and author. Loc. cit is used in place of ibid when the reference is not only to the work immediately preceding it, but also refers to the same page. Loc. cit is also used in place of op. cit when reference is made to a work previously cited and to the same page in that work. As such, Loc. cit is never followed by a volume or page number.

4. Supra

Supra means above, and it is an academic and legal citation signal used when a writer desires to refer a reader to an earlier cited authority. For example, an author wanting to refer to refer to a source or authority in his or her third footnote would cite: see supra note 3. Supra can also be used to provide a short form citation to an earlier (but ot immediately preceding) authority. The use of supra should be done with care and only when the user fully understands its usage as it could be confusing to readers if not properly used.

5. Infra

Infra means below, and it is used to indicate that the details or citation of a case will come later on in the brief or book.

6. Op. Cit.

This is an abbreviation of the Latin phrase Opera citato, which means “in the work cited”. It is used in an endnote or footnote to refer the reader to a previously cited work standing in for the full title of the work but in a different page. Thus, op cit refers the reader to the bibliography where the full citation of the work can be found or to a full citation given in a previous footnote. Op. cit. is never to be used on its own, which would make the work meaningless, but is instead usually used with the author’s name or another brief clue as to which work is referred to.