′ Prime Symbol
The prime (′) marks a derivative (f′), a transformed or transposed variable (A′), and the feet-and-minutes unit — it is a slanted mark, not an apostrophe.
Also known as: prime symbol, prime character, symbol for prime, feet and inches symbol, minutes symbol.
Codes
| Symbol | ′ | |
| Double prime (inches, seconds) | ″ · U+2033 | |
| Unicode | U+2032 | |
| HTML entity (named) | ′ | |
| HTML entity (decimal) | ′ | |
| HTML entity (hex) | ′ | |
| CSS | \2032 | |
| LaTeX | \prime | |
| Windows Alt code | Alt + 8242 |
How to type ′ (Prime Symbol)
Alt + 8242 works in apps that accept decimal-Unicode Alt input (Word among them). There is no short Alt code — the prime is outside the legacy code pages, so in other apps use Win + . (period) or copy ′ above. Double prime ″ is Alt + 8243.
No default keystroke. Open Character Viewer (Control + Cmd + Space) and search “prime”, or copy ′ above.
Type 2032, then press Alt + X to convert it to ′ (2033 then Alt + X gives ″). Turn off AutoFormat’s “smart quotes” first, or Word will convert a typed ' into a curly ’ instead.
Insert → Special characters, then search “prime”.
In math mode a plain apostrophe already renders as a prime: f'(x) and f''(x). \prime is the explicit character, used when you need it as a superscript, e.g. A^{\prime}.
Usage
- In calculus, f′(x) is the first derivative and f″(x) the second — read “f prime” and “f double prime”.
- As a unit mark, ′ is feet and ″ is inches (5′ 10″), and in angles ′ is arcminutes and ″ arcseconds — so a latitude reads 40° 26′ 46″.
- In statistics and econometrics, A′ is the transpose of A (the same thing engineers write Aᵀ); in some set-theory texts A′ is the complement of A; and in general x′ is “a modified version of x”.
- Which one to use — this is the mistake almost everyone makes: ′ (U+2032 PRIME) is upright-slanted and is the correct character. ' (U+0027) is the straight typewriter apostrophe, and ’ (U+2019) is the curly right single quote that word processors autocorrect to. Writing 5’ 10” for a height is typographically wrong; it should be 5′ 10″.