A reader recently asked if the abbreviation “id.” should be italicized and should the “I” be capitalized or not?
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According to The Bluebook, id. is always italicized (including the period). Whether it is capitalized or not will depend on where it falls. If it is part of a sentence or a citation and doesn’t start the sentence or citation, it is a small “i” as in “See id.” Where it starts a sentence or citation, it is a capital “i” as in “Id. at 635.” There is more helpful information about id. in a blog post entitled Latin, Italics, And Punctuation.
Thank you for your question!