"Rehema is a woman."
Translation:Rehema ni mwanamke.
What machieng said! ^
The reason for it is that mwanamke is a compound noun made of mwana meaning "child" (ie. offspring), but basically just meaning "person" in compounds, + mke meaning wife.
mwana+mke = wife+person = woman
The plural form of both of them is used to make the plural of the whole compound:
wana+wake = wives+people = women