This is the 8013th most frequent Polish word.
narwi
"Narwi" is the locative or vocative form of "Narew," which is a river in Poland and Belarus.
Here, 'Narwi' is used in the genitive case to refer to the name of the Narew River.
Podczas wyprawy kajakowej płynęliśmy wzdłuż Narwi.
During the kayaking trip, we paddled along the Narew River.
In this sentence, 'Narwij' is used as an imperative verb meaning 'tear off'.
Narwij tę kartkę z notesu, jeśli jej potrzebujesz.
Tear off this sheet from the notebook if you need it.
In this usage, 'Narwią' is in the instrumental case, referring to the Narew River.