The virgule punctuation mark, sometimes called a slash or a forward slash, has a few standard uses in English, plus many other common uses that aren’t considered standard by English grammar authorities.
The established uses of virgules include the following:
- They’re used in web addresses and file paths (e.g., https://grammarist.com, c:/Program Files/Google Chrome/Chrome.exe).
- They separate lines of poetry quoted without line breaks (e.g., Glory be to God for dappled things / For skies of couple-colour as a brinded cow; / For rose-moles all in stipple upon trout that swim … ).
- A virgule separates the numerator and the denominator in a fraction (e.g., ¾).
But the virgule appears in many additional, informal uses, including the following:
- It’s often used to mean per—for example, 99 miles/hour.
- It’s often used to mean and/or (as in and/or itself)—for example, “… our Federal Highway Administration hosted forums in Denver, Phoenix, Louisville/New Albany, Hartford and Brooklyn/Queens … “ (Frost Illustrated)
- It’s sometimes used to indicate a dichotomy or a vague disjunction between two things—for example, “Its appeal cuts across the usual liberal/conservative line.” (Patriot Post) An en-dash would be conventional in these cases, but people love using the virgule this way, so we should probably accept it.
File paths in Windows can use either a forward slash or a backslash, but backslash is preferred version in English locales. (For historical reasons, Japanese Windows installations write “C:¥Program Files¥Google Chrome” etc.) Unix systems always use forward slash, and the web inherited this convention from them. Modern Macs uses OS X, which is a hybrid of the NeXT Unix system and the old Mac OS, so they allow two different path separators, forward slash and (from the old Mac OS) colon. “Macintosh HD:Applications:Google Chrome.app” and “/Applications/Google Chrome.app/” refer to the same location.
>> An en-dash would be conventional in these cases, but people love using the virgule this way, so we should probably accept it.
A virgule better indicates (visually) a dichotomy of parties whereas an en-dash seems to indicate a union of the two sides.
I assume the backslash is a computer invention; I had never seen it used anywhere prior to their advent.
I am in the voice business, reading scripts for a living; too many lazy writers, especially in corporate communications, use virgules instead of appropriate words. As the joke in the business goes, “How do you pronounce the slash?”