Numeral:
A numeral is a symbol or name that stands for a number.
Examples: 3, 49 and twelve are all numerals.
So the number is an idea, the numeral is how we write it.
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Number:
A number is a count or measurement that is really an idea in our minds.
We write or talk about numbers using numerals such as "4" or "four".
But we could also hold up 4 fingers, or tap the ground 4 times.
These are all different ways of referring to the same number.
There are also special numbers (like π (Pi)) that can't be written exactly, but are still numbers because we know the idea behind them.