Numbers and symbols

First, we have to distinguish the difference between numbers and the symbols we use to represent numbers. A number is a mathematical quantity, usually correlated in electronics to a physical quantity such as voltage, current, or resistance. There are many different types of numbers. Here are just a few types, for example:
WHOLE NUMBERS:
1, 2, 3, 4, 5, 6, 7, 8, 9 . . .

INTEGERS:
-4, -3, -2, -1, 0, 1, 2, 3, 4 . . .

IRRATIONAL NUMBERS:
(approx. 3.1415927), e (approx. 2.718281828), square root of any prime

REAL NUMBERS:
(All one-dimensional numerical values, negative and positive, including zero, whole, integer, and irrational numbers)

COMPLEX NUMBERS:
3 - j4 , 34.5 6 < 20