Saturday, 10 July 2021


Coined by Welsh mathematician and physician Robert Recorde (*1512 – †1558), the equal sign (see also) entered common parlance on this day in 1557, and while not inventing +, he introduced the addition sign to England at the same time.
Wanting to avoid repetition in his treatise The Whetsome of Witte, he refers to the shorthand expression of balance as Gemowe lines—twin ones from Latin gemellus, Gemini. Appointed Comptroller of Mines and Monies under Edward VI and Queen Mary in Ireland, Recorde suffered libel from suit of a political enemy and died in a debtors’ prison, but not before leaving a legacy including authoritative works on algebra and geometry as well as the frequently cited Urinal of Physick.