"She is the only child"

Translation: Yeye ni mtoto pekee

[Gazelle1596]

This is another good example of the usage of "pekee" (vs. "peke ya...") - it mostly translates as "only" as an adjective, while "peke ya~" is by oneself. ;)
(Yes, I just wrote here instead of the original discussion where peke vs. pekee started.)

[TessEwing1]

Would "anakuwa" work instead of "wewe ni"? If not, why not?

[ElMeuNom]

I think that the present tense of kuwa is always ni. It is irregular. In every other tense, it is normal. But I don't think you can ever use the "regular" present tense of kuwa.

[TessEwing1]

Asante

[AGreatUserName]

You can use it but then it means "become(s)", not "is/am/are"

[Angela34194]

What about: yeye ni mtoto wa pekee?

[Katie105911]

I don't feel "yeye" is necessary here. "Ni mtoto pekee" should be accepted. This would be particularly true in a context such as "Tatu alifiwa na mama yake. Ni mtoto wa pekee" in other words, Tatu was bereaved of her mother [Tatu's mother died]. She is the only child.