In fact, an em is a typographical unit of measurement.) (A common myth holds that the en dash is, in fact, the width of a typesetter’s letter “N,” whereas the em dash is the width of the letter “M”-thus their names. The en dash is slightly longer than the hyphen but not as long as the em dash. Typically the writer is telling the reader that the information being set off by em dashes is important. Em dashes draw attention to the information they enclose or set apart. Parentheses tend to downplay an idea they suggest that the information in them is helpful but not necessary. If a comma (or a pair of them) works, use it. Em Dashes, Parentheses, or Commas?Ī good rule of thumb is to reserve em dashes for those places where the comma simply doesn’t provide a strong enough break. If we had used a hyphen in place of each dash two sentences ago, it would seem as though we had hyphenated two pairs of words in the sentence: “tablets-all” and “course-for,” neither of which makes any sense. If we confuse the em dash with the hyphen, we make a sentence virtually impossible to read. We bought markers, paper, pens, and tablets-all of which were on sale, of course-for our clients to use in the courtroom.We can use these dashes in pairs, as we would use parentheses-that is, to enclose a word, or a phrase, or a clause (as we’ve done here)-or they can be used alone to detach one end of a sentence from its main body.ĭashes are particularly useful in a sentence that is long and complex or in one that contains a number of commas, as in this example: We use the em dash to create a strong break in the structure of a sentence. It is significantly longer than the hyphen. When we hear the term dash, most of us picture the em dash. Here, however, our focus is on the two kinds of dashes. Elsewhere on this site, we discuss the use of hyphens to create compound words and hyphenated adjectives. On computer keyboards, the hyphen appears on the bottom half of the key located on the top row between the “0” and the equals mark (=).Ĭorrect hyphenation is often a complicated issue.