Perhaps, this paper will help: http://citeseer.nj.nec.com/62964.html

Eduardo Ochs wrote:

...

Frank Atanassow wrote:

A monad on category C is a monoid in the category of endofunctors on C.

Is that simple enough? ;)

Uh-oh. I'm a junior categorist and toposopher and I confess that all my few attempts to understand what Haskell's monads have to do with the categorical notion of a monad have failed more or less miserably. Can someone point me to a relevant paper, or give a quick explanation?