The Slash: Rules for Use

What is a slash?

The slash is used in several situations and performs various functions in written content. Above all, it can replace certain conjunctions (such as or), separate alternatives (and/or) and stand in for the preposition “per” (for example, km/h).

Using a slash also requires knowledge of certain editorial rules concerning spaces. In some cases, a space is used after the slash, or before and after it, for example, in phrase-level alternatives. In other cases, no space should be inserted, as in and/or.

When should you use a slash?

You probably use slashes fairly often, relying entirely on intuition. But are you sure you are using them correctly?

In English, there are several common situations in which a slash is appropriate.

1. Replacing “or”. A slash separates alternative words or phrases, for example, high/low and up/down.
2. Combining “and” and “or”, for example, blue and/or grey and by train and/or bus.
3. Indicating consecutive periods, for example, the 2022/23 academic year and 19th/20th-century art.
4. Marking line breaks in a quoted passage of poetry when the lines are presented continuously, for example: “Shall I compare thee to a summer’s day? / Thou art more lovely and more temperate.”
5. Replacing “per” in numerical values, for example, 10 g/l and 90 km/h.
6. Writing common fractions, for example, ¼ of a shift and ¾ of a cup.
7. Separating elements in addresses or property identifiers, where the relevant address format uses a slash, for example, 10/4 High Street.
8. Describing document and reference numbers, for example, reference no. AB 17/16 and document ref. XN 106/17.
9. Indicating foreign abbreviations, for example, c/o (“care of”) and a/a (“ad acta”, meaning “to the files”).
10. Separating numbers in a double issue of a publication, for example, issue 2/3, or other bibliographical designations such as no. 3/2019.

When should you avoid a slash?

A slash is sometimes used incorrectly, particularly in situations that resemble those in which its use is appropriate. This makes mistakes easy to make. You can avoid them by following the rules below.

Incorrect uses of the slash:

• Replacing a hyphen in a compound name, for example, Kaye/Godwin — WRONG! (correct: Kaye-Godwin);
• Writing mixed numbers with a slash, for example, 1 ¼ should be set using a proper fraction, with the numerator and denominator formatted as superscript and subscript characters;
• Replacing “and” in a compound expression when a hyphen or the word “and” is required, for example, research/development — WRONG! where research and development or research-and-development is intended;
• Creating informal abbreviations from ordinary English words, for example, Dept/Marketing — WRONG! (correct: Dept of Marketing or Marketing Department).

Slash with or without spaces: the rules

In some cases, using a slash requires a space next to it, while in others no space is used. It may seem especially confusing that a space can appear not only after the slash but also before it. However, the rules are simpler than they may first appear.

You only need to remember three rules about spacing:

• do not use spaces when a slash separates individual numbers or words, for example, up/down and 2022/23;
• use spaces when the slash separates longer phrases, for example, bank transfer / credit card, or when it marks a line break in a quoted poem: “Shall I compare thee to a summer’s day? / Thou art more lovely and more temperate”;
• you may use a space after the slash or on both sides of it, depending on the context. The important thing is to be consistent throughout the text.