Plus and minus signs

The Plus (+) and minus (-) signs are used universally to represent the operations of addition and subtraction, and have been extended to many other meanings, more or less analogous.

Though the signs now seem as familiar as the alphabet or the Hindu-Arabic numerals, they are not of great antiquity. The Egyptian hieroglyphic sign for addition, for example, resembled a pair of legs walking from right to left (the direction in which the language was written), with the reverse sign indicating subtraction. In Europe in the early 15th century the letters P and M were generally used.

The earliest appearance of the modern signs seems to come from a book by Johhannes Widman in 1489. The + is a simplification of the Latin "et" (comparable to the ampersand &). The - may be derived from a tilde written over m when used to indicate subtraction; or it may come from a shorthand version of the letter m itself.

The simple expression "one plus one" (1+1) can mean many different things, depending on the mathematical system under consideration. Many algebraic structures have some operation which is called, or equivalent to, addition, and an element called, or equivalent to, one. Moreover, the symbolism has been extended to operations that are not mathematical, such as concatenation of strings of characters.

Modulo 2/XOR      1+1=0

Binary OR/AND     1+1=1

Binary            1+1=10

Golden mean base  1+1=10.01

Balanced ternary  1+1=11

Negabinary        1+1=110

Binary i-1 base   1+1=1100

Decimal           1+1=2

Biology           1+1=3 to many

String literal    "1"+"1"="11" (concatenation)

See also

• Equals sign
• Table of mathematical symbols