Traits and Haskell type-classes

At this level of abstraction we focus on the common characteristics and ignore (abstract away) the differences and the irrelevant details.

Traits and type-classes are composable (can be mixed in).

OO Classes correspond to a too rigid and crude categorical thinking, while traits are composition of behaviors or characteristics in a proper duck-typing.

And, of course, implementing interfaces of a type-class is the same concept defined in different terms (well, type-classes).

Both are named sets of interfaces to be implemented to become an $X$.

To be an $X$ is to be able to do this and that or to have such and such characteristics.

And we are back to fundamental Set unions instead of rigid class hierarchies.