This is the 8547th most frequent German word.
kloster
Monastery.
Here, 'Kloster' refers literally to a monastery, a religious building inhabited by monks or nuns, giving a specific location context.
Das Kloster liegt auf einem Hügel.
The monastery is situated on a hill.
In this case, 'Klöster' is the plural of 'Kloster', and the context deals with their role in hospitality and lodging.
Viele Klöster bieten Gästen Übernachtungsmöglichkeiten an.
Many monasteries offer accommodation for guests.
Here, 'Kloster' is used in its singular form to describe a specific place visited during someone's travels.