Because it’s in the definite form.
- Ett stort nöjesfält.
- Det stora nöjesfältet.
Yes but why "stora"? That makes it look like a plural... How would you say "big amusement parks"? Tack.
Stora is either the plural form, or the definite form. ’Big amusement parks’ would be stora nöjesfält.
See the 'tips and notes' section of 'Adjectives 1'. They provided a good summary with examples.
The "ö" in nöjesfältet sound like something weird that I cannot describe. As if it is a different vowel completely. I guess it's due to the way it is combined with j afterwards.