This is the 14907th most frequent Polish word.
rezerwowego
"Rezerwowego" means "reserve" or "substitute" in English.
In this sentence, 'rezerwowy' is used as an adjective to describe a player as being part of the reserve squad.
Piłkarz rezerwowy wszedł na boisko w drugiej połowie.
The substitute football player entered the field in the second half.
Here, 'rezerwowego' acts as an adjective referring to a plan that was kept in reserve.
Podczas wakacji korzystaliśmy z rezerwowego planu podróży.
During the holidays, we used the backup travel plan.
'Rezerwowe' is used as an adjective describing a place that has been reserved, emphasizing availability for occupation.