Is it "djuret" with -t instead of "djuren" with -n, because it's an ett-word?
Yes, exactly.
And "djuren" exists as well and means "the animals".
Okay, tack!
Why can't it be 'De se djuret'?
"Se" is the infinitive form: att se - to see "Ser" is the present tense: jag/du/han/hon/den/det/vi/ni/de ser
It is a strong/irregular verb: jag ser - jag såg - jag har sett (I see - I saw - I have seen)
Oh, I see! Thanks. (Can you say: 'Jag ser!', as in 'I understand'? Or should you just use 'Jag förstå')