This is the 10428th most frequent Swedish word.
klassrummen
"The classrooms."
The word "klassrummen" is used here as the definite plural form of "klassrum", meaning "the classrooms", indicating specific classrooms that were cleaned.
Klassrummen städades av städarna efter lektionerna.
The classrooms were cleaned by the janitors after the lessons.
"Klassrummen" refers again to specific identified classrooms in the definite plural form, reflecting the object of the students' observation.
Eleverna ansåg att klassrummen behövde bättre ventilation.
The students thought that the classrooms needed better ventilation.
In this context, "klassrummen" is used in its definite plural form to identify certain classrooms where the activity of decorating took place.