Even Versus Odd

The simplest explanation of an even number is it's divisible by $2$ -- you can separate it into two equal halves.

The simplest explanation of an odd number is it's NOT divisible by $2$ -- you cannot separate it into two equal halves. 

Of course on the number line, you see the integers like this:

$...even, odd, even, odd, even, odd, even, odd...$