"A river has good water"
Translation:Mto una maji mazuri
u- for singular, i- for plural.
Exceptions -- animals, for example, use a- and wa- (and generally follow M/Wa grammar, taking only the pluralisation rules from their noun class). Same goes for most people words that aren't in the M/Wa class already (like daktari).
Be warned, U/N singular also uses u-. Nothing else uses i- in the plural, but N/N uses it in the singular, so don't use the subject prefix alone to guess the class of a noun. It is a bit confusing at first, but once you get them all mapped out you should get the hang of it.
One moment, please. I am not such a avanced but.... this " una" it should to be conjugation of verb with a personal pronoun. So, the river - 3th person singular it is " a " + verb " na" makes - ana. Is it possible that this sentence came to me too early ? But for a while at my level of learning I can not to agree with this grammar form.