Replies:
Yes. But then what do you mean by 'number'? There's a lot of different
kinds of numbers: natural numbers, whole numbers, rational numbers etc.
Zero isn't a natural number. Natural numbers are defined as 'the number
of elements in certain sets' so to speak without getting too technical.
All the other kinds of numbers come from our algebraic needs: the whole
numbers arise from the need to be able to subtract any two numbers, the
rationals from the need to divide numbers. The reals were invented
because some calculations couldn't be performed with rational numbers
alone.

Hm... that was a lot of talk. I hope some of it was useful to you :-)

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