olemus
objektorienteeritud keeltes: objekti tüübi kirjeldamine mitte ta klassi, vaid meetodite ja atribuutide põhjal
= in object-oriented languages: the description of the type of an object not by its class, but by its methods and attributes

ülevaateid
https://en.wikipedia.org/wiki/Duck_typing

https://devopedia.org/duck-typing

https://ericlippert.com/2014/01/02/what-is-duck-typing/comment-page-1/