This is the 15029th most frequent German word.
seitlichen
"Seitlichen" means "lateral" or "side" in English, depending on context.
The word 'seitlichen' here is used as an adjective modifying 'Fenster', describing their position as located on the sides.
Die seitlichen Fenster bieten einen schönen Ausblick.
The side windows offer a beautiful view.
In this sentence, 'seitlichen' is an adjective modifying 'Wänden', referring to their orientation on the sides.
Er befestigte die Regalhalterungen an den seitlichen Wänden.
He attached the shelf brackets to the side walls.
Here, 'seitlicher' describes the direction or orientation of the wind, indicating it comes from the side.