IO is just one example of a monad. (It might be called the "canonical" example, since monads provide a very neat functional solution to the highly non-function

IO is just one example of a monad. (It might be called the "canonical" example, since monads provide a very neat functional solution to the highly non-function problem of interacting with the real world.) Other examples include lists and functions. (Anything which satisfies the monad laws can be called a monad, there isn't any restriction or definition other than that.)