A single character standing for a number. In the decimal system (base 10) it always stands for a single numerical character: 0,1,2,3,4,5,6,7,8 or 9.
But that need not always be the case. For example, B is the hexadecimal digit representing 11.
A number
It means having more than one digit. In the context of decimal integers it means a number greater than 9.
the digit before the decimal point in decimal notation, representing an integer less than ten.
Short
I am not sure if this is what you mean but a mill is sometimes a short word for a million. One million- 1,000,000
Math is short for mathematics; this word is based on the Greek mathema meaning learning, study, science. It developed to specifically mean the science of calculation in the sense we use it today.
It is a long A. A short A would be like in the word 'math' or like in 'cat'.
what does key mean in math
Thirty thousand
a
about
Approximately