This is the 1580th most frequent Russian word.
следующей
The Russian word "следующей" means "next" or "following" in English.
Here, the word "следующей" is used as an adjective in the instrumental case, describing "недели" (week), meaning "next."
Она отложила поездку до следующей недели.
She postponed the trip until next week.
Here, "следующей" is in the prepositional case, modifying "комнате" (room), and it refers to something sequentially adjacent.
В следующей комнате идут ремонтные работы.
Renovation work is ongoing in the next room.
In this sentence, "следующей" is used as an adjective in the prepositional case, qualifying "остановке" (stop), again meaning "next" as in something immediately following in sequence.