This is the 466th most frequent Danish word.
engelske
"Engelske" means "English" (adjective, plural or definite form in Danish).
Here, 'engelske' acts as an adjective qualifying 'bøger' (books), indicating origin or related language.
De engelske bøger er meget interessante.
The English books are very interesting.
In this sentence, 'engelske' describes 'venner' (friends), indicating their nationality.
Hendes venner er engelske og bor i London.
Her friends are English and live in London.
'Engelske' functions as an adjective for 'tekster' (texts), describing their language of composition.