This is the 787th most frequent Polish word.
grudniu
"Grudniu" is the locative case of "grudzień," meaning "December" in Polish.
The word 'grudniu' is the locative case of 'grudzień,' specifying the time when the action takes place.
W grudniu często pada śnieg.
In December, it often snows.
The word 'grudniu' provides temporal context, situating the plan within a specific period (the end of December).
Pod koniec grudnia planujemy wyjazd.
At the end of December, we plan a trip.
Here, 'grudniu' indicates the specific month referenced in time, placed in locative case with the preposition 'w'.