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Prime (mark)

Punctuation marks
apostrophe (' ) parentheses ( ( ) ), brackets ( [ ] ); ( { } ); ( < > ) colon ( : ) comma ( , ) dash ( ‒ ); ( – ); ( — ); ( ― ) ellipsis ( … ) ( ... ) exclamation mark ( ! ); ( ¡ ! ) full stop/period ( . ) hyphen ( - ); ( ‐ ) interrobang ( ‽ ) question mark ( ? ); ( ¿ ? ) quotation marks ( ‘ ’ ); ( “ ” );     ( ‚ ’ ); ( „ ” ); ( ‚ ‘ ); ( „ “ );     ( ‹ › ); ( « » ); ( › ‹ ); ( » « );     ( 「 」 ); ( 『 』 ) semicolon ( ; ) slash ( / ) and backslash ( \ ) space (   ) and interpunct ( · )
ampersand ( & ) asterisk ( * ) and dagger ( † ‡) bullet ( •, more ) commercial at ( @ ) number sign ( # ) prime ( ′ ) and double prime (″) tilde ( ~ ) underscore ( _ ) vertical bar / pipe ( | )

This article is not about the symbol for the set of prime numbers, ℙ.

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The prime (′, Unicode 0x2032, ′) is not an apostrophe (', Unicode 0x0027) or an acute accent (´, Unicode 0x00B4). It has several uses:

• In set theory, A′ is the complement of the set A.
• A′ can mean a point related to A (e.g. by a transformation T).
• f′(x) is the first derivative (or derived function) of f(x).
• 42′ can mean 42 arcminutes (or sometimes, 42 minutes of time).
• 7′ can mean 7 feet.
• The prime can be used in the transliteration of some languages, such as Russian, where it is sometimes used to denote palatalization.

The double prime (″, Unicode 0x2033, ″) is not a quotation mark (", Unicode 0x0022), and is equivalent two prime characters. It is used for similar purposes:

• f″(x) is the second derivative of f(x).
• 42″ can mean 42 arcseconds (or sometimes, 42 seconds of time, e.g. on some digital cameras).
• 7″ can mean 7 inches.

The triple prime (‴, Unicode 0x2034) can mean the third derivative of a function. Similarly, the quadruple prime (⁗, Unicode 0x2057) can mean the fourth derivative of a function. Not all Web browsers can display these symbols.

To avoid counting the number of primes, the notation f⁽ⁿ⁾(x) can be used to mean the nth derivative of f(x) when n is large.

Prime and double prime are often approximated by normal or italic apostrophes and quotation marks, (' or ', " or "), especially when the character set used does not include the prime or double prime character (e.g. ISO-Latin-1 is commonly assumed on IRC).

References: (rather large)