# Definition:Equals/Historical Note

## Historical Note on Equals

The **equals sign** was introduced by Robert Recorde in his 1557 work:

*The Whetstone of Witte, whiche is the seconde parte of Arithmeteke: containing the extraction of rootes; the cossike practise, with the rule of equation; and the workes of Surde Nombers.*

Placing two hyphens together, one above the other, he wrote:

- "To avoide 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 lines of one lengthe: $= \!\!\! = \!\!\! = \!\!\! = \!\!\! =$, bicause noe .2. thynges, can be moare equalle."

The word **gemowe** comes from the Latin **geminus** meaning **twin**.

François Viète used the symbol $\sim$, while René Descartes used $\propto$.

Both were in due course supplanted by $=$. It is suggested by some sources that this was mainly through the influence of Leibniz.

## Sources

- 1992: George F. Simmons:
*Calculus Gems*... (previous) ... (next): Chapter $\text {A}.19$: Leibniz ($1646$ – $1716$) - 2008: Ian Stewart:
*Taming the Infinite*... (previous) ... (next): Chapter $4$: Lure of the Unknown - 2009: Ian Stewart:
*Professor Stewart's Hoard of Mathematical Treasures*:*Who Invented the Equals Sign?*