I don't think that is necessarily a dynamic language thing: that seems like your regular ad hoc polymorphism. Pascal allows it, IIIRC. So does C#. Being able to

I don't think that is necessarily a dynamic language thing: that seems like your regular ad hoc polymorphism. Pascal allows it, IIIRC. So does C#. Being able to use a function on different kinds of arguments is orthogonal to the typing discussion. Scheme, for example, is dynamic yet very monomorphic. You have length (working only on lists), string-length, vector-length, bytevector-length etc.