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Percent sign  ( Mathematical Symbols )

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The percent (per cent) sign ( %) is the symbol used to indicate a , a number or as a fraction of 100. Related signs include the (per thousand) sign ‰ and the (per ten thousand) sign ‱ (also known as a ), which indicate that a number is divided by one thousand or ten thousand respectively. Higher proportions use parts-per notation.

Correct style

Spacing
English style guides prescribe writing the number and percent sign without any space between. Guardian and Observer style guide.

Publication Manual of the American Psychological Association. 1994. Washington, DC: American Psychological Association, p. 114. Merriam-Webster's Manual for Writers and Editors. 1998. Springfield, MA: Merriam-Webster, p. 128.Jenkins, Jana et al. 2011. The IBM Style Guide: Conventions for Writers and Editors. Boston, MA: Pearson Education, p. 162.Covey, Stephen R. FranklinCovey Style Guide: For Business and Technical Communication. Salt Lake City, UT: FranklinCovey, p. 287.Dodd, Janet S. 1997. The ACS Style Guide: A Manual for Authors and Editors. Washington, DC: American Chemical Society, p. 264. However, the International System of Units and ISO 31-0 standard prescribe a space between the number and percent sign,

in line with the general practice of using a non-breaking space between a and its corresponding unit of measurement.

Other languages have other rules for spacing in front of the percent sign:

• In and in , the percent sign is spaced with a non-breaking space if the number is used as a noun, whereas no space is inserted if the number is used as an adjective (e.g. “a 50% increase”).
• In , the percent sign is always spaced, and a case suffix can be attached to it using the colon (e.g. 50 %:n kasvu 'an increase of 50%').
• In , the percent sign must be spaced with a non-breaking space.
• In , the percent sign is never spaced.
• In , the percent sign must always be spaced now, as almost every other symbol.
• In , the percent sign is rarely spaced, contrary to the guidelines of the GOST 8.417-2002 state standard.
• In , the percent sign is almost never spaced, probably because Chinese does not use spaces to separate characters or words at all.
• According to the Swedish Language Council, the percent sign should be preceded by a space in , as all other units.
• In , the space is prescribed by the regulatory body in the national standard DIN 5008.
• In and other , the percent sign precedes rather than follows the number, without an intervening space.
• In texts, the percent sign may either precede or follow the number, in either case without a space.
• In , the percent sign follows the number; as Arabic is written from right to left, this means that the percent sign is to the left of the number, usually without a space.
• In , the percent sign precedes the number without intervening space; as Hebrew is written from right to left, this means that the percent sign is written to the right of the number, just as in English.

Usage in text
It is often recommended that the percent sign only be used in tables and other places with space restrictions. In running text, it should be spelled out as percent or per cent (often in newspapers). For example, not "Sales increased by 24% over 2006", but rather "Sales increased by 24 percent over 2006". American Economic Review: Style Guide UNC Pharmacy style guide University of Colorado style guide

Evolution
Prior to 1425 there is no known evidence of a special symbol being used for percentage. The term per cento, "for a hundred", was used as well as several different abbreviations (e.g. "per 100", "p 100", "p cento", etc.). Examples of this can be seen in the 1339 arithmetic text (author unknown) depicted below. The letter p with its crossed by a horizontal or diagonal strike conventionally stood for per, por, par, or pur in Mediaeval and Renaissance palaeography. Letter p. / Cappelli, Adriano: Lexicon Abbreviaturarum. 2. verb. Aufl. Leipzig 1928. Wörterbuch der Abkürzungen: P. pages 256–257

At some point a scribe of some sort used the abbreviation "pc" with a tiny loop or circle (depicting the ending -o used in Italian numeration for primo, secondo, etc.) This appears in some additional pages of a 1425 text which were probably added around 1435. This is shown below (source, Rara Arithmetica p. 440).

The "pc" with a loop eventually evolved into a horizontal fraction sign by 1650 (see below for an example in a 1684 text) and thereafter lost the "per".

In 1925 D.E. Smith wrote, "The solidus form () is modern." in Dover reprint of 1958,

Usage

Encodings

Unicode
The code points are:
• ("The following sections present the complete lists of character entity references." ("percnt;").),
• ,
• a.k.a. , and

There is also , which has the circles replaced by square dots set on edge, the shape of the digit 0 in .

ASCII
The for the percent character is 37, or 0x25 in .

In computers
Names for the percent sign include percent sign (in ), , grapes (in hacker ), and the humorous double-oh-seven (in ).

In , the percent character is also used for the in programming languages that derive their syntax from the C programming language, which in turn acquired this usage from the earlier B.

In the textual representation of URIs, a % immediately followed by a 2-digit number denotes an octet specifying (part of) a character that might otherwise not be allowed in URIs (see ).

In , the percent sign is a wildcard character in "LIKE" expressions, for example &amp;percnt; will fetch all records whose names start with "Lisa ".

In (and therefore also in LaTeX) and , and in and , a % denotes a line comment.

In , a trailing % after a variable name marks it as an .

In % is the sigil for .

In many programming languages' string formatting operations (performed by functions such as ), the percent sign denotes parts of the template string that will be replaced with arguments. (See printf format string.) In Python and Ruby the percent sign is also used as the string formatting operator.

In the command processors COMMAND.COM (DOS) and CMD.EXE (OS/2 and Windows), %1, %2,... stand for the first, second,... parameters of a . %0 stands for the specification of the batch file itself as typed on the command line. The % sign is also used similarly in the FOR command. %VAR1% represents the value of an environment variable named VAR1. Thus:

```set PATH=c:\;%PATH%
```
sets a new value for PATH, that being the old value preceded by "c:\;". Because these uses give the percent sign special meaning, the sequence %% (two percent signs) is used to represent a literal percent sign, so that:
```set PATH=c:\;%%PATH%%
```
would set PATH to the literal value "c:\;%PATH%".

In the , % is part of the default command prompt.

In linguistics
In linguistics, the percent sign is prepended to an example string to show that it is judged well-formed by some speakers and ill-formed by others. This may be due to differences in or even individual . This is similar to the to mark ill-formed strings, the to mark strings where well-formedness is unclear, and the to mark strings that are syntactically well-formed but semantically nonsensical.

Notes
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