Language Interoperability is that classes written in one language should be able to talk directly to classes written in another language.

• A class written in one language can inherit from a class written in another language.

• The class can contain an instance of another class, no matter what the languages of the two classes are.

• An object can directly call methods against another object written in another language.

• Objects (or references to objects) can be passed around between methods.

• When calling methods between languages we can step between the method calls in the debugger, even when this means stepping between source code written in different languages.