a x b = b + ... +b is not a strict definition, it's just a convention. Check the English Wikipedia: https://en.wikipedia.org/wiki/Multiplication https://en.wi

a x b = b + ... +b is not a strict definition, it's just a convention. Check the English Wikipedia: https://en.wikipedia.org/wiki/Multiplication https://en.wikipedia.org/wiki/Multiplication It's, as you say, 5x3 = 3 + 3 + 3 + 3 +3. But now check Russian Wikipedia: https://ru.wikipedia.org/wiki/%D0%A3%D0%BC%D0%BD%D0%BE%D0%B6%D0%B5%D0%BD%D0%B8%D0%B5 https://ru.wikipedia.org/wiki/%D0%A3%D0%BC%D0%BD%D0%BE%D0%B6... There you'll see 5x3 = 5 + 5 + 5. So much for the "very well-defined mathematical meaning".