So for example, there's many ways of defining functions. You could say something like f of x is equal to x squared. So that means that whatever x, whatever you input into the function, the output is going to be that input squared. You could have something defined like this. F of x is equal to x squared if x odd, and you could say it's equal to x to the third otherwise. So if it's an odd integer, it's an odd integer, you just square it, but otherwise for any other real number, you take it to the third power. This is a valid way of defining a function.