The plus and minus signs (+ and −) are mathematical symbols used to represent the notions of positive and negative as well as the operations of addition and subtraction. Their use has been extended to many other meanings, more or less analogous. Plus and minus are Latin terms meaning "more" and "less", respectively.

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 in the direction in which the text was written (Egyptian could be written either from right to left or left to right), with the reverse sign indicating subtraction:^{[citation needed]}

In Europe in the early 15th century the letters "P" and "M" were generally used. The symbols (P with line p̄ for piú, i.e., plus, and M with line m̄ for meno, i.e., minus) appeared for the first time in Luca Pacioli’s mathematics compendium, Summa de arithmetica, geometria, proportioni et proportionalità, first printed and published in Venice in 1494. The + is a simplification of the Latin "et" (comparable to the ampersand &).^{[citation needed]} 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.^{[citation needed]} In his 1489 treatise Johannes Widmann referred to the symbols − and + as minus and mer (Modern German mehr; "more"): "das − ist, das ist minus, und das + ist das mer".

Plus may refer to:

A sign is a representation of an object that implies a connection between itself and its object. A natural sign bears a causal relation to its object—for instance, thunder is a sign of storm. A conventional sign signifies by agreement, as a full stop signifies the end of a sentence. (This is in contrast to a symbol which stands for another thing, as a flag may be a symbol of a nation).

The way a sign signifies is called semiosis which is a topic of semiotics and philosophy of language.

How a sign is perceived depends upon what is intended or expressed in the semiotic relationship of:

Thus, for example, people may speak of the significance of events, the signification of characters, the meaning of sentences, or the import of a communication. Different ways of relating signs to their objects are called modes of signification.

Uses of conventional signs are varied. Usually the goal is to elicit a response or simply inform. That can be achieved by marking something, displaying a message (i.e. a notice), drawing attention or presenting evidence of an underlying cause (for instance, medical symptoms signify a disease), performing a bodily gesture, etc.