This is the 2517th most frequent Russian word.
пятом
"Пятом" is the prepositional case, singular form of "пятый," meaning "fifth" in English.
Here, "пятом" denotes the ordinal number 'fifth' in the instrumental case, referring to the location 'on the fifth floor'.
На пятом этаже находится кафе.
There is a café on the fifth floor.
In this sentence, "пятом" is used as an ordinal number 'fifth', indicating a specific position as in 'fifth seat'.
Мы были в кинотеатре на пятом месте.
We were seated in the fifth row in the cinema.
Here, "пятом" signifies the ordinal 'fifth' referring to the school grade 'fifth grade'.