Multiplication sign

"×" redirects here. It is not to be confused with the letter X.
"Times sign" redirects here. It is not to be confused with sign of the times.
×
Multiplication sign
The multiplication sign

The multiplication sign or times sign is the symbol ×. The symbol is similar to the lowercase letter x but is a more symmetric saltire, and has different uses. It is also known as St. Andrew's Cross[1] and dimension sign.

Uses

In mathematics, the symbol × (read as times or multiplied by) is primarily used to denote the

In biology, the multiplication sign is used in a botanical hybrid name (botany), for instance Ceanothus papillosus × impressus (a hybrid between C. papillosus and C. impressus) or Crocosmia × crocosmiiflora (a hybrid between two other species of Crocosmia). However, the communication of these hybrid names with a standard non-multiplication "x" is common when the actual "×" symbol is not readily available.

The multiplication sign is also used by historians for an event between two dates. When employed between two dates, for example 1225 and 1232, 1225×1232 means "no earlier than 1225 and no later than 1232". It can also be used in a date range: 1225×1232–1278.[2]

History

The × symbol for multiplication was introduced by William Oughtred in 1631.[3] It was chosen for religious reasons to represent the cross.[4]

Similar notations

The letter "x" is sometimes used in place of the multiplication sign. This is considered incorrect in mathematical writing.

In algebraic notation, widely used in mathematics, a multiplication symbol is usually omitted wherever it would not cause confusion: "a multiplied by b" can be written as ab or a b.

Other symbols can also be used to denote multiplication, often to reduce confusion between the multiplication sign × and the commonly used variable x. In many non-Anglophone countries, rather than ×, the primary symbol for multiplication is U+22C5 ⋅ DOT OPERATOR, for which the interpunct · may be substituted as a more accessible character. This symbol is also used in mathematics wherever multiplication should be written explicitly, such as in "ab = a⋅2 for b = 2"; this usage is also seen in English-language texts. In some languages (especially Bulgarian) and French the use of full stop as a multiplication symbol, such as a.b, is common.

In programming languages, the standard notation of multiplication operator is U+002A * ASTERISK due to traditional restriction of all syntax of computer languages to the ASCII character repertoire.

In computer software

The × symbol is listed in the Latin-1 Supplement character set and is U+00D7 × MULTIPLICATION SIGN (HTML × · ×) in Unicode. It can be invoked in various operating systems as per the table below.

The × symbol is used by the APL programming language to denote the sign function.

There is a similar character ⨯ at U+2A2F, but this is not always considered identical to U+00D7, as U+2A2F is intended to explicitly denote the cross product of two vectors.

Mac OS X in Character Palette, search for MULTIPLICATION SIGN[5][6]
HTML, SGML, XML × and ×
Microsoft Windows
  • Alt Gr+
  • Alt+0215
  • Alt+0D7[7]
Unix-like
OpenOffice.org times
TeX \times
Unicode U+00D7

Unicode

Other variants are encoded:

See also

References

  1. ↑ Stallings, L. (2000). "A Brief History of Algebraic Notation". School Science and Mathematics 100 (5): 230–235. doi:10.1111/j.1949-8594.2000.tb17262.x. ISSN 0036-6803.
  2. ↑ New Hart's rules: the handbook of style for writers and editors, Oxford University Press, 2005, p. 183, ISBN 978-0-19-861041-0
  3. ↑ Florian Cajori (1919). A History of Mathematics. Macmillan.
  4. ↑ Stallings, L. (2000). "A Brief History of Algebraic Notation". School Science and Mathematics 100 (5): 230–235. doi:10.1111/j.1949-8594.2000.tb17262.x. ISSN 0036-6803.
  5. ↑ http://www.apple.com/de/pro/tips/specialchar.html Apple Sonderzeichen (German / Deutsch)
  6. ↑ http://www.typografie.info/typowiki/index.php?title=Mac_Zeichenpalette
  7. ↑ http://www.fileformat.info/info/unicode/char/00D7/index.htm

External links

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