Equal sign

The mathematician Robert Recorde ( 1510 - 1558 ) created the equal sign in modern form in his work The Whetstone of Witte (1557). He justified the use of two parallel strokes as follows (the spelling of the original is Early New English): "... bicause noe 2 thynges can be moare equalle", that is, "no other two things can be more equal." Prior to this, in ancient and medieval mathematics, equality was denoted verbally (for example, est egale ). In the 17th century, Rene Descartes began to use æ (from Latin aequalis ) when recording, and he used the modern equal sign to indicate that the coefficient can be negative. Francois Viet equals deduction. The symbol of the record was not immediately spread. In continental Europe, the “=” sign was introduced by Leibniz only at the turn of the XVII-XVIII centuries, that is, more than 100 years after the death of Robert Record, who first used it for this.

• “≠”, “! =” Or “<>” are not equal.
• “ ≈ ” - “approximately equal”. It is used in the designation of two quantities, the difference between which in this task can be neglected.
• “ ≃ ” - used to denote homeomorphic spaces in topology .
• “~” - “ asymptotically equal ”, “ proportionally ”. Sometimes used to indicate the proportionality of two quantities or similarities in geometry.
• "≡" - "identically equal." It is used to denote two identical (equal for any values ​​of input parameters) expressions. Also for comparison modulo .
• “: =” - often used to denote the assignment operator , as well as, along with “≜” and “≝” for equality by definition.
• “ ≌ ” - is used to denote congruent figures in geometry and diffeomorphic manifolds in differential geometry .
• “ ≅ ” - is used in the absence of full lexical or stylistic correspondence of a foreign word or expression and its Russian translation equivalent ^[1] .

In programming languages, the = symbol = most often used for comparison and / or assignment operations. In some languages ​​(e.g. Basic ), the symbol is used for both operations, depending on the context. In C , PHP , etc., = means assignment, equality is written as == . In Perl , in addition, the operators for comparing strings are different from the operators for comparing numbers, the equality of strings is checked by eq . In Pascal , by contrast, = stands for equality; assignment stands for := .

• New large English-Russian dictionary: in 3 volumes / Apresyan Yu. D. , Mednikova E.M. , Petrova A.V. et al. Under the general. hands. Yu. D. Apresyan. - 1st ed. - M .: Russian language , 1993. - T. I: A — F. - 832 s. - ISBN 5-200-01954-0 .

• Robert Recorde invents the equals sign
• History of Equal Sign (German)