There are two main uses of the plus sign ``$+$ '' (which is a simplified form of ``SPMamp;'') 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.: $$a\!+\!b\; := \mbox{\, the sum of\, } a \mbox{\, and\, }b$$
• There is also a special use for the unary operation identity mapping concerning numbers and other ring elements: $$+a\; :=\; a \mbox{\; (for all } a)$$