What this aspect is: whenever you compare something over something else, you have a rate. Damage per second, damage taken per second, healing per second, damage per GCD, etc. these are all rates.

What it looks like: x/y=z z is a rate, with units of x per y (or xpy, if you make an acronym out of it)

While you won't necessarily find rates (z) inside of equations, the goal of most wow math is to determine some sort of a rate. They are the easiest aspect to start out with, but can become more complex once other aspects are introduced in to finding a given rate.

Time is fat, and checks it's weight on a timescale:

And because time is fat, it's on the bottom of the equation in most cases because it doesn't like to crush its friends.

Most rates involve time in some way shape or form. How you express time is VERY important to the result of your calculations.
Note: When ever I say "on an infinite time scale", that means as time approaches infinity, the DPS of the ability average out to be what ever the answer happens to be.
The hardest part of dealing with time that most people have is figuring out how much time to use in your equation.

for all of these examples I will be using DPS equations, though you can apply this to any form of a rate equation.

The Basic Idea:
Damage/ usage= DPS

Divide how much damage an ability does by how often you use it. (this can be longer than the cooldown if it is not your highest priority ability, so make sure your usage is accurate)
Let's say you have an instant ability that does 1500 damage with no cooldown. If