The plus sign and the minus sign are mathematical symbols used to denote positive and negative functions, respectively. In addition, + represents the operation of addition, which results in a sum, while − represents subtraction, resulting in a difference. Their use has been extended to many other meanings, more or less analogous. Plus and minus are Latin terms meaning "more" and "less", respectively.
From Johannes Widmann's book on "handy and pretty arithmetic for all merchants"
Addition is one of the four basic operations of arithmetic, the other three being subtraction, multiplication and division. The addition of two whole numbers results in the total amount or sum of those values combined. The example in the adjacent image shows two columns of three apples and two apples each, totaling at five apples. This observation is equivalent to the mathematical expression "3 + 2 = 5".
Part of Charles Babbage's Difference Engine including the addition and carry mechanisms
A circular slide rule