Hyphens and Dashes

Hyphens, en and em dashes are among the most misunderstood, and misused, punctuation marks in typography. While their appearance is generally similar, they have distinct designs and serve specific functions. These three marks are not interchangeable, and knowing the difference is key to setting type correctly.

The hyphen is the shortest of the three marks, and is used to hyphenate a word at the end of a line by breaking after a syllable. Hyphens are also used to join separate words into a compound word, such as dyed–in–the–wool; and to separate the digits in phone and account numbers. A hyphen can be designed as a simple horizontal stroke, or it can have characteristics that match the rest of the typeface.

The en dash is longer than the hyphen and shorter than the em dash. It is used to indicate a duration of time (also referred to as a span or a range) such as Monday - Friday, 9am - 5pm, often replacing prepositions such as “to” and “through”. Historically, the en dash was half the length of the em dash, but today both marks vary in relative length from typeface to typeface. The best–looking en dashes are frequently designed to approximate the width of the cap or lowercase N, which makes them proportionally pleasing to the overall width of the particular typeface.

The em dash is the longest of the three marks, and is used to indicate a break in thought, or to set off a thought within a thought. Historically (particularly in metal type), the em dash was the length of the em square in a given point size of type, except for some condensed designs which had shorter dashes. (An em is a unit of measure equal to the width of the point size of type; thus, an em dash in 18 point type often was 18 points long.) In subsequent font technologies, including phototype and digital type, this absolute standard ceased to exist, and the length of the dash varied from typeface to typeface. In fact, many type and design professionals think em dashes look best when their length approximates the width of the cap or lowercase M, in proportional harmony to the overall width of the typeface design. NOTE: Using two hyphens instead of an em dash is typographically incorrect. This treatment is a holdover from the typewriter, which offers no dash on the keyboard.

Be sure to search for any double hyphens and other misuses of hyphens and/or dashes, and to replace them with the correct punctuation. That said, you may exercise artistic license regarding dashes if their width or spacing seems out of proportion or otherwise inharmonious. For instance, when the em dash seems too wide for the typeface, some designers replace it with an en dash. Another stylistic preference is to add extra space before and after either the en or em dash if it appears too close to neighboring characters. In fact, some designers prefer the addition of a full word space before and after an en dash. Whatever your personal preferences, remember to apply them consistently throughout.

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• Editor’s Note:Ilene Strizver, founder of The Type Studio, is a typographic consultant, designer and writer specializing in all aspects of typographic communication. She conducts Gourmet Typography workshops internationally. Read more about typography in her latest literary effort, Type Rules! The designer's guide to professional typography, 4th edition, published by Wiley & Sons, Inc. This article was commissioned and approved by Monotype Imaging Inc.