This is the 6492nd most frequent Polish word.
cmentarnej
"Of the cemetery" or "cemetery's" (possessive form).
Here, 'cmentarnej' is used as an adjective modifying 'alejki' (alley) to describe a path belonging to or located in a cemetery.
Spacerowaliśmy ścieżką cmentarnej alejki.
We walked along the path of a cemetery alley.
'Cmentarnej' modifies 'kaplicy' (chapel), describing that the chapel is associated with a cemetery.
Historia starej kaplicy cmentarnej jest naprawdę fascynująca.
The history of the old cemetery chapel is truly fascinating.
In this sentence, 'cmentarnej' modifies 'posesji' (property), indicating that the property in question belongs to or is adjacent to the cemetery.