Editing Niger–Congo languages (section)

==== Nasality ====
Several scholars have documented a contrast between oral and [[nasal vowel]]s in Niger–Congo.<ref>le Saout (1973) for an early overview, Stewart (1976) for a diachronic, Volta–Congo wide analysis, Capo (1981) for a synchronic analysis of nasality in Gbe (see [[Gbe languages#Nasality in Gbe|Gbe languages: nasality]]), and Bole-Richard (1984, 1985) as cited in Williamson (1989) for similar reports on several Mande, Gur, Kru, Kwa, and Ubangi languages.<!-- the Bole-Richard citations are: Bole-Richard, Rémy (1984) 'Le nghwla, langue sans consonne nasale. CIRL 16:23–35 and Bole-Richard, Rémy (1985) 'Hypothèse sur la genèse de la nasalité en Niger–Congo', JWAL 15, 2, 3-28. --></ref> In his reconstruction of proto-Volta–Congo, Steward (1976) postulates that [[nasal stop|nasal consonants]] have originated under the influence of nasal vowels; this hypothesis is supported by the fact that there are several Niger–Congo languages that have been analysed as lacking nasal consonants altogether. Languages like this have nasal vowels accompanied with [[complementary distribution]] between oral and nasal consonants before oral and nasal vowels. Subsequent loss of the nasal/oral contrast in vowels may result in nasal consonants becoming part of the phoneme inventory. In all cases reported to date, the bilabial /m/ is the first nasal consonant to be phonologized. Niger–Congo thus invalidates two common assumptions about nasals:<ref>As noted by Williamson (1989:24). The assumptions are from Ferguson's (1963) 'Assumptions about nasals' in Greenberg (ed.) ''Universals of Language'', pp 50–60 as cited in Williamson art.cit.</ref> that all languages have at least one primary nasal consonant, and that if a language has only one primary nasal consonant it is /n/.

Niger–Congo languages commonly show fewer nasalized than oral vowels. [[Kasem language|Kasem]], a language with a ten-vowel system employing ATR vowel harmony, has seven nasalized vowels. Similarly, [[Yoruba language|Yoruba]] has seven oral vowels and only five nasal ones. However, the language of [[Zialo language|Zialo]] has a nasal equivalent for each of its seven oral vowels.