The equals sign or equality sign, =, is a mathematical symbol used to indicate equality in some well-defined sense.[1][2] It was invented in 1557 by Robert Recorde. In an equation, the equals sign is placed between two expressions that have the same value, or for which one studies the conditions under which they have the same value. In Unicode and ASCII, it has the code point 3D.
The etymology of the word "equal" is from the Latin word "æqualis",[3] as meaning "uniform", "identical", or "equal", from aequus ("level", "even", or "just").
The = symbol, now universally accepted in mathematics for equality, was first recorded by Welsh mathematician Robert Recorde in The Whetstone of Witte (1557).[4] The original form of the symbol was much wider than the present form. In his book Recorde explains his design of the "Gemowe lines" (meaning twin lines, from the Latin gemellus[5]
And to auoide the tediouſe repetition of theſe woordes : is equalle to : I will ſette as I doe often in woorke vſe, a paire of paralleles, or Gemowe lines of one lengthe, thus: =, bicauſe noe .2. thynges, can be moare equalle.[6]
"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" (History of Mathematics, University of St Andrews).[7]
In mathematics, the equals sign can be used as a simple statement of fact in a specific case (x = 2
), or to create definitions (let x = 2
), conditional statements (if x = 2, then ...
), or to express a universal equivalence ((x + 1)² = x² + 2x + 1
).
The first important computer programming language to use the equals sign was the original version of Fortran, FORTRAN I, designed in 1954 and implemented in 1957. In Fortran, = serves as an assignment operator: X = 2
sets the value of X
to 2. This somewhat resembles the use of = in a math
The etymology of the word "equal" is from the Latin word "æqualis",[3] as meaning "uniform", "identical", or "equal", from aequus ("level", "even", or "just").
The = symbol, now universally accepted in mathematics for equality, was first recorded by Welsh mathematician Robert Recorde in The Whetstone of Witte (1557).[4] The original form of the symbol was much wider than the present form. In his book Recorde explains his design of the "Gemowe lines" (meaning twin lines, from the Latin gemellus[5]
And to auoide the tediouſe repetition of theſe woordes : is equalle to : I will ſette as I doe often in woorke vſe, a paire of paralleles, or Gemowe lines of one lengthe, thus: =, bicauſe noe .2. thynges, can be moare equalle.[6]
"The symbol = was not immediately popular. The symbol || was used by some and æ (or œ), from the Latin word aequalis meaning equal, w
The = symbol, now universally accepted in mathematics for equality, was first recorded by Welsh mathematician Robert Recorde in The Whetstone of Witte (1557).[4] The original form of the symbol was much wider than the present form. In his book Recorde explains his design of the "Gemowe lines" (meaning twin lines, from the Latin gemellus[5]
And to auoide the tediouſe repetition of theſe woordes : is equalle to : I will ſette as I doe often in woorke vſe, a paire of paralleles, or Gemowe lines of one lengthe, thus: =, bicauſe noe .2. thynges, can be moare equalle.[6]
"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" (And to auoide the tediouſe repetition of theſe woordes : is equalle to : I will ſette as I doe often in woorke vſe, a paire of paralleles, or Gemowe lines of one lengthe, thus: =, bicauſe noe .2. thynges, can be moare equalle.[6]
"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" (History of Mathematics, University of St Andrews).[7]
Instead of a double hyphen, the equals sign is sometimes used in Japanese as a separator between names. In Ojibwe, the readily available equal sign on a keyboard is used as a substitute for a double hyphen.
In linguistic interlinear glosses, an equals sign is conventionally used to mark clitic boundaries: the equals sign is placed between the clitic and the word that the clitic is attached to.[16]
In
In chemical formulas, the two parallel lines denoting a double bond are commonly rendered using an equals sign.
In Morse code, the equals sign is encoded by the letters B (-...) and T (-) run together (-...-).[citation needed] The letters BT stand for Break Text, and are put between paragraphs, or groups of paragraphs in messages sent via Telex,[citation needed] a standardised tele-typewriter. The sign, used to mean Break Text, is given at the end of a Morse code, the equals sign is encoded by the letters B (-...) and T (-) run together (-...-).[citation needed] The letters BT stand for Break Text, and are put between paragraphs, or groups of paragraphs in messages sent via Telex,[citation needed] a standardised tele-typewriter. The sign, used to mean Break Text, is given at the end of a telegram to separate the text of the message from the signature.[18][better source needed]
The symbol used to denote inequation (when items are not equal) is a slashed equals sign ≠ (U+2260). In LaTeX, this is done with the "\neq" command.
Most programming languages, limiting themselves to the 7-bit ASCII character set and typeable characters, use ~=
, !=
, /=
, or <>
to represent their Boolean inequality operator.
The triple bar symbol ≡ (U+2261, LaTeX \equiv) is often used to indicate an identity, a definition (which can also be represented by U+225D ≝ EQUAL TO BY DEFINITION or U+2254 ≔ COLON EQUALS), or a congruence relation in modular arithmetic.[1]
~=
, !=
, /=
, or <>
to represent their Boolean inequality operator.
The triple bar symbol ≡ (U+2261, LaTeX \equiv) is often used to indicate an identity, a definition (which can also be represented by U+225D ≝ EQUAL TO BY DEFINITION or U+2254 ≔ COLON EQUALS), or a congruence relation in modular arithmetic.[1]
Equali
Equality of truth values (through bi-implication or logical equivalence), may be denoted by various symbols including =, ~, and ⇔.
=
· =
)Related:
≠
· ≠, ≠
)