7 Italic, roman, and other type treatments
In word processor files, do not use underlining when italic is intended. Underlining text on hard copy or proofs indicates that it is to be set in italics. When underlining matter in this way, ensure that the underlining includes all matter that is to be italicized, but nothing else. Mistakes are particularly common with internal and surrounding punctuation. Consider:
‘The novel Bell, Book, and Candle’, not ‘The novel Bell, Book, and Candle’
‘The colours were red, white, and blue’, not ‘The colours were red, white, and blue’
In typeset material it is undesirable to use underlining, as it cuts through the descenders of the characters and in some typefaces may obscure the identity of similar letters (g and q, for example). Italic type is preferable as a distinguishing mark, though in some cases underlining is required or is uniquely useful—for example in some scientific and mathematical notation, or in the precise reproduction of a manuscript, inscription, or correspondence, where it is needed to approximate underlining in the original.
As underscoring on hard copy or proofs indicates to the typesetter that italic is wanted, any instances where underlining is required must be marked in a different way: for example, with a highlighted underscore, which can be explained to the designer and typesetter in a note.
In non-print contexts such as websites avoid underlining as a substitute for (or in addition to) italics to indicate work titles or for emphasis, as users expect underlining to indicate a hyperlink. Browsers have their own styles for the display of hyperlinks so it is not necessary to add underlining to links in copy.