This is the 248th most frequent Swedish word.
söndagen
"The Sunday."
In this sentence, 'söndagen' refers to a recurring event happening every Sunday in general.
På söndagen brukar jag alltid gå till parken.
On Sundays, I usually go to the park.
Here, 'söndagen' refers to a specific Sunday in the past.
Förra söndagen hade vi en familjemiddag.
Last Sunday, we had a family dinner.
In this example, 'söndagen' denotes a specific upcoming Sunday.