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.
In Mabaan, a Western Nilotic language, there are several singular and plural number suffixes. However, many singular nouns have no segmentally distinct suffix, but have a root-final nasal which corresponds to a root-final homorganic plosive in the plural. The plosive is the original alternant, as can be determined on Mabaan-internal grounds as well as by a comparison of Mabaan with other Western Nilotic languages. The nasal alternant of a root-final plosive is a reflex of a former singular suffix with an alveolar nasal. As evidenced by Mayak, another Western Nilotic language, this suffix was an innovation, and it came to be used both in nouns that had no number suffix originally and as an additional suffix in nouns with a singulative suffix. A similar development seems to have taken place in plural nouns, in that a velar plosive suffix is now found in many plural nouns that were presumably morphologically unmarked originally. There is evidence that the new suffixes are Stage III articles. Thus, there are two historical layers of number inflection in Mabaan, a phenomenon somewhat reminiscent of the situation in the Southern Nilotic languages.