Verbal suffixes and suffix reduction in Surkum and other Northern Burun languages: Interaction with focus

Surkum and other languages belonging to the Northern Burun branch of Western Nilotic have a word-final verbal suffix (with several allomorphs) which does not contribute to the propositional content of the sentence. It is obligatory in, for instance, affirmative declarative clauses with the verb in final position, while it is precluded in, for instance, negative clauses, constituent questions and cleft sentences. Thus, this “affirmative” suffix is in complementary distribution with explicitly or inherently focalized constituents or elements. Therefore, it is arguably a grammatically controlled focus marker which obligatorily focalizes the verb or the polarity whenever nothing else is in focus.