This is the 157th most frequent Polish word.
lipca
"Lipca" means "July" in Polish, in the genitive case.
"lipca" is used as "lipcu" here, modified to denote something occurring in the context of the month of July.
W lipcu często pada deszcz.
In July, it often rains.
"lipca" denotes the genitive case, specifying the date within the month of July.
Piętnastego lipca odbędzie się koncert.
On the fifteenth of July, there will be a concert.
"lipca" denotes the genitive case, used to specify the location within the month, as part of an expression.