This is the 2942nd most frequent Polish word.
nerek
The Polish word "nerek" is the genitive plural form of "nerka," which means "kidney."
In this sentence, "nerek" is used in the context of human anatomy, referring to kidneys.
Moje nerek są zdrowe i dobrze funkcjonują.
My kidneys are healthy and functioning well.
Here, "nerek" refers to kidneys again, but in the context of medical or scientific research.
Podarowałem swoje stare książki fundacji na rzecz badania pracy nerek.
I donated my old books to a foundation researching kidney function.
In this usage, "nerek" pertains to kidneys concerning personal health and wellbeing.