(Note: italicize punctuation following italicized words, with the exception of brackets.)
1. To emphasize a particular word in its context. Use sparingly, not for whole sentences.
e.g. That’s not a rhetorical question.
2. To draw attention to an unusual word or one being used in an unusual way.
3. To indicate internal dialogue in contrast to verbal discourse.
e.g. We headed upstairs. It’s so hot up here, I thought to myself.
4. To highlight key terms or words that are the focus of discussion. Usually italicized on first appearance only.
e.g. The word freedom means different things to different people.
5. To highlight foreign words (including Japanese) which appear occasionally and aren’t used commonly in English. (If a word is familiar to most readers and listed in Merriam-Webster’s, do not use italics). If used repeatedly throughout an article, a term may be italicized only on its first occurrence. (CMOS 7.49)
Note: If used in a context with a less familiar term, either both or neither should be italicized, for internal consistency. (CMOS 7.52)
e.g. Closer inspection revealed that some of the revisions were quite minor, for example replacing a word in hiragana with kanji or changing the punctuation.
OR: Closer inspection revealed that some of the revisions were quite minor, for example replacing a word in hiragana with kanji or changing the punctuation.
6. With titles of books/compositions/publications, and official legal names (legislative acts and statutes, court cases, etc.).
Note: Titles of individual programs not in continuing series are set in non-italicized type and enclosed in quotation marks. (See Names: Associations, Committees, Conferences, Seminars, etc., 2.)
7. For special vehicle names.
8. To set off single letters against accompanying words.
e.g. “Mind your ps and qs.”