An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The symbol + indicating summation or a positive quantity. The sign is believed to be a shortened form of the L. word et denoting "and" which was the term for addition. The signs + and - first appeared in an arithmetic book by Johannes Widmann entitled Behennde und hübsche Rechnung, published in Leipzig in 1489.

→ plus; → sign.