The equal sign, equals sign, or "=" is a mathematical symbol used to indicate equality. It was invented in 1557 by Welshman Robert Recorde. The equals sign is placed between the things stated to be equal. In many computer programming languages == is a boolean logic binary relation representing equality. ... In mathematics, a binary relation (or a dyadic relation) is an arbitrary association of elements of one set with elements of another (perhaps the same) set. ... A definition is a concise statement explaining the meaning of a term, word or phrase. ... Double hyphen in the Fraktur typeface. ... In mathematics, a set of symbols is frequently used in mathematical expressions. ... In mathematics, two mathematical objects are considered equal if they are precisely the same in every way. ... Events Spain is effectively bankrupt. ... National motto: Cymru am byth (Welsh: Wales for ever) Waless location within the UK Official languages English and Welsh Capital Cardiff Largest city Cardiff First Minister Rhodri Morgan Area  - Total Ranked 3rd UK 20,779 km² Population  - Total (2001)  - Density Ranked 3rd UK 2,903,085 140/km² NUTS... Robert Recorde (c. ...

History

A common equation, featuring the equals sign.

The "=" symbol that is now universally accepted in mathematics for equality was first used by Welsh mathematician Robert Recorde in The Whetstone of Witte (1557). The original form of the symbol was much wider (longer) than the present form. In his book[1], Recorde explains his design: to auoide the tediouse repetition of these woordes: is equalle to : I will sette as I doe often in woorke use, a paire of paralleles, or Gemowe [i.e. "twin"] lines of one lengthe, thus: =, bicause noe .2. thynges, can be moare equalle. However, a manuscript from the University of Bologna, dated from 1550–1568, features the same equality symbol, possibly earlier than Recorde's use.^{[citation needed]} According to Scotland's St Andrews University Maths History website[2], "The symbol '=' was not immediately popular. The symbol || was used by some and æ (or œ), from the Latin word aequalis meaning equal, was widely used into the 1700s." Image File history File links 2+2. ... Image File history File links 2+2. ... This article is about the country. ... Leonhard Euler, one of the greatest mathematicians of all time A mathematician is a person whose primary area of study and research is the field of mathematics. ... Robert Recorde (c. ... Events Spain is effectively bankrupt. ... Motto (Latin) No one provokes me with impunity Cha togar mfhearg gun dioladh (Scottish Gaelic) Wha daur meddle wi me?(Scots)1 Anthem (Multiple unofficial anthems) Scotlands location in Europe Capital Edinburgh Largest city Glasgow Official languages English, Gaelic and Scots1 Government Constitutional monarchy  -  Monarch Queen Elizabeth II... University of St Andrews The University of St Andrews was founded between 1410-1413 and is the oldest university in Scotland and the third oldest in the United Kingdom. ... For a list of biographies of mathematicians, see list of mathematicians. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Events and trends The Bonneville Slide blocks the Columbia River near the site of present-day Cascade Locks, Oregon with a land bridge 200 feet (60 m) high. ...

Related symbols

A symbol used to denote items that are approximately equal is "≈" (wave lines), and the symbol used to denote when items are not equal is "≠" (slashed equal sign). Most programming languages, which are limited to the ASCII character set, use "~=", "!=", "=/=" or "<>" to represent "not equal to"; "!=" has carried over into newsgroups and Internet forums. The symbol "≡" is often used to indicate an identity, or a congruence relation in modular arithmetic. The symbol "≘" can be used to express that an item corresponds to another. It has been suggested that this article or section be merged with estimation. ... A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. ... Image:ASCII fullsvg There are 95 printable ASCII characters, numbered 32 to 126. ... A newsgroup is a repository usually within the Usenet system, for messages posted from many users at different locations. ... This article does not cite any references or sources. ... In mathematics, the term identity has several important uses: identity can refer to an equality that remains true regardless of the values of any variables that appear within it, to distinguish it from an equality which is true under more particular conditions. ... In mathematics and especially in abstract algebra, a congruence relation or simply congruence is an equivalence relation that is compatible with some algebraic operation(s). ... Modular arithmetic (sometimes called modulo arithmetic, or clock arithmetic because of its use in the 24-hour clock system) is a system of arithmetic for integers, where numbers wrap around after they reach a certain value — the modulus. ...

In programming languages, the equals sign may either denote a boolean operator to test equality of values (sometimes a double equal sign "=="), or it may denote an assignment (sometimes denoted with a colon-equals ":="). In some programming languages such as PHP a triple equal sign ("===") denotes equivalence[3], meaning that not only do the two values parse to be the same, they are of the same data type. (For instance, in many scripting languages ("0 == false") is true, but ("0 === false") is not.) In logical calculus, logical operators or logical connectors serve to connect statements into more complicated compound statements. ... This article does not cite any references or sources. ... The colon (:) is a punctuation mark, visually consisting of two equally sized dots centered on the same vertical line. ... PHP is a reflective programming language originally designed for producing dynamic web pages. ...

Equality of truth values, i.e. bi-implication or logical equivalence, may be denoted by various symbols including =, ~, and <=>. It has been suggested that this article or section be merged into Logical biconditional. ... In logic, statements p and q are logically equivalent if they have the same logical content. ...

See also

• Equality (mathematics)
• Logical equality
• Plus and minus signs
• Double hyphen
• 2+2=5

In mathematics, two mathematical objects are considered equal if they are precisely the same in every way. ... XNOR Logic Gate Symbol Logical equality is a logical operator that corresponds to equality in boolean algebra and to the logical biconditional in propositional calculus. ... The plus and minus signs (+ and −) are used to represent the notions of positive and negative as well as the operations of addition and subtraction. ... Double hyphen in the Fraktur typeface. ... The phrase two plus two make five (or 2 + 2 = 5) is sometimes used as a succinct and vivid representation of an illogical statement, especially one made and maintained to suit an ideological agenda. ...

References

• Cajori, Florian (1993). A History of Mathematical Notations. New York: Dover (reprint). ISBN 0-486-67766-4. 
• Boyer, C. B.: A History of Mathematics, 2nd ed. rev. by Uta C. Merzbach. New York: Wiley, 1989 ISBN 0-471-09763-2 (1991 pbk ed. ISBN 0-471-54397-7)

External links

• Earliest Uses of Symbols of Relation
• Image of the page of The Whetstone of Witte on which the equal sign is introduced
• Scientific Symbols, Icons, Mathamatical Symbols