"It is the official flag."
Translation:Det er det officielle flag.
What is wrong with "det er det officiellt flag"? Adjectives are supposed to agree with the nous, right? And flag is neuter and the adjective takes three forms according to the hover hints, so I'm confused.
When adjectives are definite, they do not show agreement in gender. So when there's a "det" or "den" before the adjective, it usually takes -e to show definiteness and cannot have any -t. I hope it makes sense :) It's also confusing because -e also means plural on adjectives.