Idem

Id. (masculine and neuter) and ead. (feminine) (Latin, short for idem and eadem, "the same") denote the previously cited source (compare ibid.). Id. is particularly used in legal citations. They are also used in academic citations replacing the name of a repeated author. Id. is used extensively in Canadian legislation to apply a short description to a section with the same focus as the previous. Id. is an abbreviation where the last two letters of the word are not present; thus, it always takes a period (or full stop) in both British and American usage.