Plus Sign (+)

The plus sign is a mathematical symbol written as two intersecting lines—one horizontal and one vertical—forming the shape "+". It most commonly denotes addition, the operation of combining two or more numbers to obtain their sum. Example: 2 + 3 = 5.

Beyond addition, the symbol is used to indicate that a number is positive, as in +7. In this usage it is called a unary operator, since it applies to a single number alone, whereas addition requires two operands.

Use in mathematics

Addition is one of the four basic operations of arithmetic, alongside subtraction, multiplication, and division. It has two important properties: commutativity (2 + 3 = 3 + 2) and associativity ((1 + 2) + 3 = 1 + (2 + 3)). Zero leaves any number unchanged when added to it, and is therefore called the additive identity.

In higher mathematics, the symbol is also used for other operations built on the concept of addition, such as vector addition, matrix addition, or addition of elements in abstract algebra. The symbol ± (plus-minus) denotes that both positive and negative solutions are possible, as in the solution of quadratic equations.

History and form

The symbol is believed to derive from an abbreviation of the Latin word "et," meaning "and." European mathematicians in the late Middle Ages used various symbols; in later centuries + and − became standard in printed mathematical texts. For a long time before that, other peoples used words or special characters instead.

Other uses

The symbol is employed in many contexts outside mathematics: international telephone numbers begin with + to indicate the country code; in computer programming + often concatenates characters or numbers; company and service names sometimes have + added to suggest an enhanced level. There are also distinct symbols resembling it with different meanings, such as the Christian cross, which differs from the plus sign in use.