"My horse is small"
Translation:Farasi wangu ni mdogo
the exception to the rule is all nouns that are human, insect or animal. While these nouns are typically associated with the M- and Wa- prefixes, not all of them follow this trend e.g. doctor (daktari - madaktari), pilot (rubani-marubani), bird (ndege-ndege) etc. However, as long as they are human, insect or animal, they will take on the prefixes associated with the M/Wa noun class, in this case wangu (for both singular and plural). There are exceptions to that rule as well i.e. some family members (mama, baba, dada, kaka, shangazi, ndugu; this list may not be extensive) whose possessive is "yangu" and "zangu", and prefixes are those of the N/N noun class... it takes a bit of time to get the hang of it
some of the noun classes have been covered more in depth here