In the code example, it'd be `Burrito` along with the `>>=` operator and `return` function. In Haskell, Monad is the type class (more or less an Interface) that specifies the types of those functions, so anything that implements Monad is said to be "a monad". F# does not have type classes, so there's not one single thing to point to in that code as a monad, only the interface being implemented as a whole.