OOP is pretty well defined.

99% of the time it means type dependent namespaces.

Class A.foo and Class B.foo both represent separate namespaces in which a field or method foo can be defined, the name space is directly tied to a type. In Haskell every function is defined in what amounts to be a global namespace. This is particularly annoying when you have records that share the same attribute names.

You might argue that structs fit this definition but they are missing type dependent namespaces for functions/methods and the fact that you can define fields and methods to only be accessible within their type dependent namespace, not outside of them.