Why is Basque mainly described as a suffixing language?

Basque is primarily characterized as a suffixing language because it predominantly appends suffixes to words to convey grammatical information, such as number and case, rather than relying on productive prefixes. While some ancient prefixes persist in the language, they are no longer considered productive in modern usage.1

This suffixing nature allows for complex grammatical structures, including the "heaping" of suffixes upon one another. For instance, genitival endings indicating possession can theoretically be added to nouns without limit, and noun suffixes can even be attached to verb forms to express the subordination of clauses. Additionally, the language utilizes a single declension system that employs suffixes or postpositions to denote specific grammatical roles.1