This is the 15339th most frequent Russian word.
потолке
"Потолке" is the prepositional case form of "потолок," meaning "ceiling."
The word "потолке" here is used in the prepositional case to indicate the location, referring to the ceiling.
На потолке висит красивая люстра.
There is a beautiful chandelier hanging on the ceiling.
In this sentence, "потолке" is also used in the prepositional case, describing the placement of the stain on the ceiling.
Я увидел пятно на потолке и решил его закрасить.
I noticed a stain on the ceiling and decided to paint over it.
"Потолке" is employed in the prepositional case, explaining where the crack appeared.