At least seven strategies for calling attention to one or more words exist, but few of them are appropriate for a document that one wishes to consider professional looking. The purposes and relative merits of various approaches are discussed below.
Styling a word, phrase, or sentence entirely in uppercase letters has limited utility: All-caps are employed either to represent speaking at a high volume (therefore, people who use all-caps in email or to comment on online content are often facetiously admonished to stop shouting) or to identify text on signage or in a notice. Assiduously avoid the style, otherwise; reading all-caps is fatiguing to the eye because readers are not used to recognizing so many capital letters in succession.
Boldface is often used for display copy (headings, subheadings, and other text other than the running text, or default wording in a piece of content); another use is to highlight introduced terms that may be defined within the text or in footnotes or a separate glossary. Some writers frame a word or phrase in asterisks to replace the boldface style; notice that in Microsoft Word, doing so will cause the enclosed text to convert to boldface. Avoid boldface for other emphatic uses.
Italics is the most frequently used type format to indicate emphasis. It is employed for foreign words and phrases that have not been adopted into English, for titles of compositions such as films and books, to represent emphatic speech (for example, in “You’re not really going to tell her, are you?”), or to refer to a word as a word (for example, “Define hubris”). The low-tech variation is to frame a word or phrase between underscores (_), but doing so in Microsoft Word will convert the text to italics.
4. Different Point Size
Text can be rendered in a larger (or smaller) point size than surrounding text to make a point, but this not recommended for most publications or documents; exceptions include advertising, lighthearted or whimsical content, or children’s books. (One can, for example, emphasize the distinction in volume between a giant or a miniature being and a normal-sized person by increasing or decreasing the size of the type used to indicate the unusually sized person’s speech.) Exceptions include footnotes, captions, and other supporting text.
5. Quotation Marks
Quotation marks are often used to bracket a word or phrase used facetiously or ironically, or to represent the writer’s skepticism or a mocking tone (for example, “The hotel’s ‘luxury’ suite was nearly indistinguishable from any ordinary accommodations”). Overuse of scare quotes, however, is distracting.
Quotation marks are often mistakenly employed when something is being identified or introduced. (For example, no quotation marks are required around the phrase “Richter scale” in the sentence “The measurement system, called the ‘Richter scale,’ is algorithmic.”) They do, however, take the place of italics in referring to a term as a term when the term consists of more than one word (or to enclose a single word used as a word when italics are not available to or are not used by a publication), as in “The phrase ‘eminent domain’ has a specific legal definition.” The similarity of purpose here is likely the cause of confusion.
6. Small Caps
Small caps are uppercase letters that are equal in height to lowercase letters; in this style, capital letters are usually represented by full-size uppercase letters. Sometimes, the first phrase or line of the first sentence of a chapter or a section of type is styled in small caps for emphasis, and small caps are occasionally employed in place of all-caps, boldface, or italics to provide distinction.
Underlining for emphasis has largely been supplanted by italics. It is now rarely used outside of instructional text to indicate blank spaces to be filled in.