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]}

— And so, to avoid the tedious repetition of these words: "is equal to" I will set as I do often in work use, a pair of parallels, or duplicate lines of one [the same] length, thus: =, because no 2 things can be more equal.

"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]}

— And so, to avoid the tedious repetition of these words: "is equal to" I will set as I do often in work use, a pair of parallels, or duplicate lines of one [the same] length, thus: =, because no 2 things can be more equal.

"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]}

— And so, to avoid the tedious repetition of these words: "is equal to" I will set as I do often in work use, a pair of parallels, or duplicate lines of one [the same] length, thus: =, because no 2 things can be more equal.

"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" (^{[6]}

— And so, to avoid the tedious repetition of these words: "is equal to" I will set as I do often in work use, a pair of parallels, or duplicate lines of one [the same] length, thus: =, because no 2 things can b## Usage in mathematics and computer programming

"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]}