You only have to define the behavior: https://en.wikipedia.org/wiki/Duck_typing https://en.wikipedia.org/wiki/Duck_typing A journalist is someone that does jo

You only have to define the behavior: https://en.wikipedia.org/wiki/Duck_typing https://en.wikipedia.org/wiki/Duck_typing A journalist is someone that does journalism, just like a runner is someone that runs. The behavior "doing journalism" is simply reporting on something to an audience.