[martincmartin]

You're right, it's not the normal definition of derivative. He's defining a function on numbers that has some similarities to the derivative (the multiplication rule is the same, and therefore so are some other properties), but isn't the derivative.

It's common in mathematics to take a word that already means something, and re-use it for a different but related concept. For example, in group and field theory, you talk about addition and multiplication, but they're not necessarily the standard definition.

[robzyb]

> It's common in mathematics to take a word that already means something, and re-use it for a different but related concept. For example, in group and field theory, you talk about addition and multiplication, but they're not necessarily the standard definition.

That's true, but I feel like the article mislead me because it didn't give me a proper and timely explanation of what it means by "derivative".

[thomasvarney723]

I find I have the same problem explaining computer technologies to people.