The plus sign symbol (+), indicates addition or a positive value. The plus sign was devised in conjunction with the minus sign (not to be confused with a hyphen) to make writing mathematical equations easier. 

Prior to the use of these signs, equations were written as word problems, which caused significant repetition problems. The plus sign represents not only addition of two numbers, but also the positivity of a number or equation. The word plus means “more” in Latin, and minus means “less.”

Although hieroglyphics existed in early Egyptian times to symbolize addition, it is not clear whether these symbols became the basis for today’s plus sign. The earliest known use was in Nicole Oresme’s manuscripts in the 14th century B.C.E.

The plus sign indicates addition between two numbers, and serves as a binary operator in most cases. It can also be a unary operator which leaves its operand unchanged. For example, +y means the same as y. The Egyptian hieroglyphic sign for addition depicted a pair of legs walking to the right, or forward (the symbol for subtraction reversed the walking direction).

In early 15th century Europe, “P” was used to indicate plus, derived from the Italian word più, meaning to add; while “M” was used to indicate minus, derived from the Italian word meno, meaning to take away.

Mathematics have been used in academic writing for centuries. The “P” and “M” were first noted in Summa de arithmetica, geometria, proportioni et proportionalità, a compendium of mathematics by Franciscan friar and Italian mathemetician Luca Bartolomeo de Pacioli, also known as the father of modern day accounting and bookkeeping. Pacioli lived from 1447 to 1517 in Florence, Italy, and died at the age of 70.

His other works included De Divina Proportione, a treatise double-entry bookkeeping. The plus sign is a derivative of the Latin “et”, meaning and which is also represented by the ampersand symbol “&.” When written over an m, the tilde signified subtraction, so the slash through the middle of the symbol may be derived from this tilde use, or from a simplified form of the letter “m” itself.

In addition to Johannes Widmann’s references to plus and minus (as mer and minus) in 1489, Henricus Grammateus used the plus and minus symbols in 1518. The British were introduced to the plus, minus, and equals sign by Robert Recorde in The Whetstone of Witte in 1557. Recorde also invented the equals sign.

The plus sign notation may be used to emphasize the positive nature of a number when presented with its negative opposite. Addition is common in many algebraic structures, and most have an operation that is the same, or similar to that of the plus sign.

The plus sign conventionally denotes only commutative operations, but its meaning can be extended to exclusive or logical disjunction operations (⨁ and ∨, respectively). A raised plus sign can also be used in elementary education to show positive or negative numbers.