How can Basque express possession with the ending -(r)en?

In the Basque language, possession is expressed using the genitive suffix -(r)en, which is appended to the noun. The parentheses indicate that the r is an optional element, typically used depending on the preceding sound.

This suffix functions similarly to the English preposition "of" in possessive constructions. Because Basque is a suffixing language, these endings can theoretically be "heaped" or stacked upon one another without limit to indicate complex possessive relationships, much like the English phrase "the button of the coat of the son of the Major of York."1