This is the 1258th most frequent Polish word.
czwartej
"czwartej" - "of the fourth" (genitive or dative singular feminine form of "czwarta").
Here, 'czwartej' refers to the ordinal aspect, indicating the fourth hour in a sequence.
Spotykamy się o czwartej godzinie.
We meet at the fourth hour.
Here, 'czwartej' denotes a specific time of day, indicating 4 PM in the afternoon.
Mam lekcje do czwartej po południu.
I have classes until 4 PM.
In this sentence, 'czwartej' is used to specify an ordinal number modifying 'stronie,' indicating the fourth one in a series.