This is the 4323rd most frequent French word.
fermées
Closed.
The word 'fermées' here is used as a past participle adjective describing the state of 'les fenêtres' being closed.
Les fenêtres sont fermées pour empêcher le bruit.
The windows are closed to prevent noise.
In this sentence, 'fermées' is used as a past participle adjective in compound past tense, indicating the state of 'les portes' before a certain event.
Les portes étaient fermées avant son arrivée.
The doors were closed before his arrival.
The word 'fermées' is used as 'fermés', another form to conform to the gender ('masculine plural') of 'les magasins', showing the physical status as 'not open'.