Op. cit.

Latin shorthand for “in the work cited.” Chicago style doesn't use it, and you should use a shortened note instead.

“Op. cit.” is short for the Latin opere citato, “in the work cited.” Older notes used it after an author’s name to point back to a source already cited in full, as in “Smith, op. cit., 45.”

Library guides to Chicago style say that Chicago doesn’t use it, and recommend against using it in assignments. The same goes for “ibid.”, which the current edition discourages. See ibid.

What to write instead. For a source you have already cited, give a shortened note: the author’s surname, a short form of the title, and the page.

2. Yu, Interior Chinatown, 112.

This shows the reader which source you mean, even if other notes come between.

Where you might see it. In older books and articles, and in some other disciplines. If you meet “op. cit.” in a source, it means “the work already cited above.” It points to a note earlier in that text. When you cite that source yourself, give its full details.

Check which notes style your instructor wants.