that's not 100% true as well, you got omega and theta and others as well for the other cases.
Edit: See http://stackoverflow.com/questions/471199/what-is-the-differ...
Edit: See http://stackoverflow.com/questions/471199/what-is-the-differ...
The S.O. link you posted contains an Accepted Answer which is also exactly correct, and happens to agree exactly with btilly.
I don't know what you think you're saying, or what you think that SO link supports. But it is NOT the case that "big O is worst-case", nor is it the case that the variants like little-o/big-theta/big-omega/etc have anything to do with best/worst/average case. The relevant sense of "upper bound" is not some kind of subtle synonym for "worst case".