This is the 12373rd most frequent Polish word.
mszę
"Mszę" means "Mass" (a Christian religious ceremony).
'mszę' is in the accusative case, showing the object of the action of going.
Dziś wieczorem idę na mszę.
This evening, I am going to mass.
'mszy' is in the genitive case, used here to show possession or description.
Nigdy nie widziałem tak pięknej mszy.
I have never seen such a beautiful mass.
'mszy' is in the locative case, indicating the location or time frame of the action.