In general, text that is in a foreign language (i.e., a language other than English or French) is set in italic type. Most commonly, Latin terms and phrases are set in italic type, unless the term or phrase has been absorbed into English (e.g., "ad hoc").
Latin terms commonly used in footnote references are set in roman type (e.g., "ibid.," "supra," "infra," "et al.").
Exception: McGill italicizes "ibid," "supra," and "infra."
For common Latin terms and their meaning, see the Emond Spelling Guide.