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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.

Programming language polymorphism means that one interface or program definition can be used with values of multiple types. In object-oriented programming, subtype polymorphism allows references with a common static type to denote instances of different concrete subclasses or implementers of a trait. An object method call uses dynamic dispatch to select the overriding implementation belonging to the receiver's runtime type. For example, different implementations of a playlist interface can respond to the same insert call without the client testing their concrete classes.

Parametric polymorphism uses type parameters, as in Sequence[A], so the same definition works uniformly for songs, integers, or other elements. Ad hoc polymorphism includes method overloading, where different parameter signatures share a name and the static types determine overload selection. These mechanisms are distinct: selecting an overloaded signature is not the same step as dispatching an override of that selected signature. Class inheritance can supply implementations, but the reusable interface and legal subtyping relationship determine what a polymorphic client may do.

Subtype polymorphism lets a reference with a common supertype denote values of different implementing classes. A call through that reference uses dynamic dispatch to select the concrete implementation.

Parametric polymorphism defines an operation or data structure using type parameters, such as a collection with an element-type parameter. Instantiations retain type information while reusing one generic definition.

Ad hoc polymorphism, commonly expressed by method overloading, gives several implementations the same name but different parameter signatures. The compiler selects a suitable overload using the available static types. This selection differs from later dynamic dispatch on the receiver of a selected instance method. A programming language can support all three in one program.