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Using an interface or definition across multiple types. Subtype polymorphism dispatches through a common supertype; parametric polymorphism uses a type parameter uniformly; method overloading selects among signatures by static types in languages such as Scala. These mechanisms should be distinguished from genetic or materials-science polymorphism.

The type assigned to a program expression during type checking. It controls which members and overloads are available at that expression. A reference with a broad static type can designate an object with a narrower runtime type; that does not expose additional overloads through the broad reference.