plus sign
There are two main uses of the plus sign “$+$” (which is a simplified form of “&”) in the mathematics and the applying sciences:

•
The original use is as the sign for the binary operation^{} addition^{} of numbers and other elements of rings and algebras, vectors, etc.:
$$a+b:=\text{the sum of}a\text{and}b$$ 
•
There is also a special use for the unary operation identity mapping concerning numbers and other ring elements:
$$+a:=a\text{(for all}a)$$
Title  plus sign 
Canonical name  PlusSign 
Date of creation  20130322 17:35:43 
Last modified on  20130322 17:35:43 
Owner  pahio (2872) 
Last modified by  pahio (2872) 
Numerical id  5 
Author  pahio (2872) 
Entry type  Definition 
Classification  msc 00A06 
Classification  msc 00A05 
Synonym  plus 
Related topic  Sum 
Related topic  SumOfSeries 
Related topic  SignumFunction 
Related topic  OppositeNumber 
Related topic  ProductOfNegativeNumbers 