 Solution

Two mechanisms are subtype polymorphism and parametric polymorphism.

With subtype polymorphism, a trait or abstract class declares an operation and concrete subclasses implement or override it. A Player reference holding a House object invokes House.play through dynamic dispatch. The client is written against the common contract.

With parametric polymorphism, a software class or generic method has a type parameter, such as List[T] or def identity[T](x: T): T = x. The same definition works for many supplied type arguments, with static relationships between input and output types. Method overloading is another mechanism, usually called ad hoc polymorphism: alternatives share a name but are selected from their parameter signatures at compile time.