"Where is the teacher?"
Translation:Mwalimu yuko wapi?
If we were to compare "Mwalimu ni shuleni." and "Mwalimu yuko shule." which one is correct? How do they contrast?
-po, -ko and -mo are locatives, think of them as the location version of "to be".
Saying "Mwalimu ni shuleni", doesn't really make sense, though people will probably understand what you mean. The sentence "Mwalimu yuko shule" isn't perfect either, as there is no preposition. So a better sentence would be
"Mwalimu yuko/yupo shuleni" (yupo implies a more specific place than yuko)
"Mwalimu yupo mbele ya shule" - The teacher is in front of the school
Therefore in a question one must always use -ko, because the place is not defined. (Otherwise you would not ask where someone/something is.)
First Mwalimu ni shuleni is not grammatical correct. it is like saying teacher is school. When you say mwalimu ni, you are defining the teacher hence the next word cannot be school. Mwalimu Yuko shule, you are suggesting where the teacher is.
The correct one is"Mwalimu yuko shule" the other one is weird, translating word to word sometimes doesn't work.
The first class (humans) uses "a-" at the beginning of verbs; "yu-" is both for demonstrative "huyu"/"yule" (this/that person) and for location such as that - unfortunately I cannot explain to you why they developed differently. or even how.