Supra

'Supra' is Latin for 'above' and, in citation, is the counterpart of 'infra' ('below'). In legal writing it directs the reader back to a source cited earlier in the document that is not the immediately preceding one (which would take 'Id.'). A typical form is 'Smith, supra note 12, at 45' — meaning 'the Smith source first cited in footnote 12, now at page 45'.

The convention is efficient because it lets a long document — a brief, a law review article, a book — refer to a source dozens of times without ever repeating the full citation. Once the source has been fully introduced, every subsequent reference is a supra pointer that leans on the earlier footnote.

Outside law, 'supra' appears in some academic humanities styles and in older scholarly editions, especially when a work needs to cross-reference itself: 'see supra, p. 42'. Modern editors often prefer plain-language cross-references ('as noted on page 42'), which serve readers who may not be familiar with the Latin apparatus.

Common mistake: using 'supra' where 'Id.' is required, or the reverse. 'Id.' is only for the immediately previous citation; 'supra' is for any earlier one that is not immediately previous. A footnote that reads 'Id., supra note 3' is redundant and technically wrong.