This is the 140th most frequent Persian word.
زیادی
"زیادی" means "too much," "excessive," or "extra" in English.
Here, 'زیادی' is used as an adjective meaning 'a large number of' to describe the quantity of pages.
این کتاب صفحات زیادی دارد.
This book has many pages.
In this sentence, 'زیادی' functions as an adverb, implying an excessive amount of the action, indicating overdoing the resting.
او زیادی استراحت میکند.
He rests too much.
Here, 'زیادی' is used to express an excessive degree, describing the crowding as more than usual or normal.