Use Prime Marks for Measurements
Prime (′) and double prime (″) marks are distinct from quotation marks and apostrophes. Use them for feet/inches, minutes/seconds, and coordinates. Never substitute curly quotes or straight quotes for primes.
Incorrect (quotes used as primes):
<p>The board is 6' 2" long.</p>
<p>The coordinates are 40° 26' 46" N.</p>Correct (true prime characters):
<p>The board is 6′ 2″ long.</p>
<p>The coordinates are 40° 26′ 46″ N.</p>Key characters:
| Character | Name | HTML Entity | Unicode |
|---|---|---|---|
| ′ | Prime (single) | ′ |
U+2032 |
| ″ | Double prime | ″ |
U+2033 |
Primes should lean slightly to the right, distinct from the curly shape of apostrophes.