This is the 1631st most frequent Polish word.
nauczyciela
"Teacher" (male or general form, genitive singular).
In this sentence, 'nauczyciela' in accusative case is used to indicate the person receiving help.
Pomogłem nauczyciela w przygotowaniu lekcji.
I helped the teacher to prepare lessons.
The word 'nauczyciela' in this sentence refers to the direct object form in accusative case.
Spotkałem swojego nauczyciela w sklepie.
I met my teacher in the store.
Here, 'nauczyciela' is used in a genitive case to indicate possession or relation associated with the friend.