Is atheism a belief?

[Whateverist]

Christianity is a religion based on faith
Agnosticism is a position based on knowledge
Atheism is a " " " " based on " " " "

You've ignored my challenge to the description you give for your own position.  I'll repeat it.

I only believe in knowledge

To which I said knowledge is usually defined as justified true belief.  Are you seriously claiming all your beliefs are knowledge based by this definition?  

Meanwhile you seem to be having trouble with the idea that a person can reasonably check both boxes: no, I hold no belief in any god; and no, I don't know if any gods actually exist.  Where is the contradiction?

If in fact your agnosticism is so pure that you feel you just can't answer the belief question, can't you see that commits you to agreeing that at this time you do not actually hold a belief in gods?  

You might object that you likewise do not hold any disbelief toward any gods.  That's fine and neither do some of us.  I'm just not one of them where supernatural, omni-powerful gods are concerned.  But since gods are mysterious if nothing else, it is always possible that those kinds of descriptions are completely off base and that whatever has given rise to god belief is something much more mundane.  The poorly defined nature of "god" is part of the reason for this mess.  Maybe once it becomes clear what we are talking about you and the rest of use will have a clearer idea in what it is we may or may not believe.