mbúla,
pl. bambula (class 9/10 (2) : - / - (ba-) : plural invariable from context (or informal/modern ba-))
mvula,
pl. bamvula (class 1a/2 : - / ba-)
mbúla,
pl. bambula (class 1a/2 : - / ba-) (informal plural)
Rain, year
vagina, in some places "mbula" also means "vagina", in this case it is better to use "mvula" to talk about the rain.