There are different schools of thought on when to use italics, but most style guides agree on a few points:
- It’s okay to occasionally use italics for emphasis, but avoid doing it too much. Instead, use sentence construction to emphasize important words.
- Italicize foreign words or phrases that are unlikely to be familiar to most of your readers. But loanwords and loan phrases that are well established in English don’t need to be italicized.
- Italicize words presented as words (e.g., the word the).
- Italicize letters presented as letters (e.g., the letter q).
- Italicize titles of publications and large works (e.g., The New York Times, Citizen Kane, Pride and Prejudice, What to Expect When You’re Expecting).
At Grammarist, to avoid a clutter of quotation marks, we use italics for quoted words and phrases and for definitions that aren’t integrated into sentences—for example:
The idiom to boot, meaning in addition to or besides, has nothing to do with footwear.
This suits our needs, but it’s by no means standard. Most publications do use italics for words presented as words, but in general they use quotation marks for quoted text.