Without context, both "the book" and "a book" are reasonable translations.
Perhaps it hadn't been added to the database when you tried. It's there now (8 March 2020).
The quiet young man ?=? the calm young man. Right or wrong? Quiet is not accepted.
Why is the l in luvenis not being pronounced?
It's not an l (Lima), it's an I (India), and it is pronounced like Y as in "yes."
Why is it wrong to say 'a book' instead of 'the book'?
"The young calm man" is correct but "The calm young man" (how we would normally order those adjectives in English) is not. Should this be adjusted?