The advantages of analyzing the Yoruba prefix "oni-" as two morphemes, "o-" and "ni-" are discussed, and it is shown why it is better to analyze it as an inseparable, single morpheme rather than two separate morphemes. "Oni-" is the only class-maintaining prefix in Yoruba, and is the only prefix attached to a noun to form another noun. Evidence is shown to support the explanation of "oni-" as a single morpheme. Many examples exist in Yoruba to show that there are nouns that have the structure "oni + x" but the "ni + x" counterparts either do not exist or sound awkward. Contains 15 references. (LB)