Definitely...or Definately?

I was just doing my math homework and as I was writing out observations of  stem plots (exciting, yes), I wrote the word definately, and paused.  Wait a second...is that right?  Without Googling or using a spell checker, right now, can you tell me, is it spelled "definately" or "definitely"?  It is definitely (or definately) not "defiantly", which I see people write a lot.  Stare at it long enough and it's hard to decide!  haha, or maybe only at 1am when all you want to do is hit the sack but still have 5 more math problems looming ahead of you PLUS another assignment (that hopefully can be done quickly).  I have a feeling this is going to be a loooong next four months and I am dreading the winter/snowy/cold/depressing part but....I ♥ to learn, remember? (see prior post)

Well, I already know the answer to this, but just checking if you did.  ;)