A number
the digit before the decimal point in decimal notation, representing an integer less than ten.
what does key mean in math
Approximately
about
a
I do not know of such a word related to math(s)
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.
many
There is no such math word, so it does not mean anything. You may wish to check your spelling before posting questions!
The word at means the least
the word by means 'times' or 'multiply'