What ″ means
It marks inches, arcseconds, or another related quantity.
After a measurement such as 5″, it supplies the unit without a word; in angular notation it follows degrees and arcminutes as the next smaller unit. In formulas, a doubled prime distinguishes a further related quantity: f″ can mark a second derivative.
As of June 2026, Option-Shift-G is listed as the Mac shortcut for this mark.
Why did its time use fade?
By 2015, use of prime marks for elapsed time had declined as word-processing systems became more widely available. For lengths and angles, the pair still separates neighboring units: ′ marks feet or arcminutes; ″ marks inches or arcseconds.
How do I type double prime?
As of June 2026, Option-Shift-G is listed as the Mac shortcut for this mark.
In HTML, ″ names the double prime; lowercase ′ names the single prime.
Many keyboards offer a straight double quote, and smart-quote settings can turn it into a curly quotation mark. Some fonts also make ″ look like a closing quote, so check the character in technical text.
Technical and deliberate; its placement makes the unit or notation clear.
Keep it out of dialogue: a measurement mark does not enclose a quotation.
What it means when someone sends it to you
3 readingsDon't confuse it with
3Questions people ask
1Can I use a double quote for inches?
Usually. Casual writing commonly uses the keyboard double quote to stand for inches. In technical typesetting, use the double prime when readers or software need to distinguish a measurement from a quotation.
How to type ″
″\2033Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.