Equals sign

[3] Diophantus's use of ⟨ἴσ⟩, short for ἴσος (ísos 'equals'), in Arithmetica (c. 250 AD) is considered one of the first uses of an equals sign.

After its introduction by Recorde, it wasn't used again in print until 1618 (61 years later), in an anonymous Appendix in Edward Wright's English translation of Descriptio, by John Napier.

It wasn't until 1631 that it received more than general recognition in England, being adopted as the symbol for equality in three influential works, Thomas Harriot's Artis analyticae praxis, William Oughtred's Clavis mathematicae, and Richard Norwood's Trigonometria.

There were several other competing symbols for equality, especially outside of England around the 16th and 17th centuries, and Recorde's version made no significant influence in the European continent until 1650 or 1660.

In In 1571 Wilhelm Xylander published an edition of Diophantus' Arithmetica in which two parallel vertical lines || were used for equality.

A major competitor to Recorde's sign was Descartes' own symbol, introduced in his La Géométrie (1637).

Descartes does not give any reason for introducing his new symbol, however Florian Cajori suggests it is because = was also being used for a difference operation at the time.

The fact that both Newton and Leibniz used Recorde's symbol led to its general adoption.

This somewhat resembles the use of = in a mathematical definition, but with different semantics: the expression following = is evaluated first, and may refer to a previous value of X.

A rival programming-language usage was pioneered by the original version of ALGOL, which was designed in 1958 and implemented in 1960.

ALGOL included a relational operator that tested for equality, allowing constructions like if x = 2 with essentially the same meaning of = as the conditional usage in mathematics.

Following ALGOL, most languages that use = for equality use := for assignment, although APL, with its special character set, uses a left-pointing arrow.

[11] The equals sign is also used as a grammatical tone letter in the orthographies of Budu in the Congo-Kinshasa, in Krumen, Mwan and Dan in the Ivory Coast.

A possibly unique case of the equals sign of European usage in a person's name, specifically in a double-barreled name, was by pioneer aviator Alberto Santos-Dumont, as he is also known not only to have often used a double hyphen ⹀ resembling an equal sign = between his two surnames in place of a hyphen, but also seems to have personally preferred that practice, to display equal respect for his father's French ethnicity and the Brazilian ethnicity of his mother.

In Ojibwe, the readily available equals sign on most keyboards is commonly used as a substitute for a double hyphen.

Equality of truth values (through bi-implication or logical equivalence), may be denoted by various symbols including =, ~, and ⇔.

If interpreted strictly as it says, it would imply that A correct version of the argument would be This difficulty results from subtly different uses of the sign in education.

Starting in algebra courses, the sign takes on a relational meaning of equality between two calculations.