This is the 105th most frequent Polish word.
wszystkie
"All" or "all of them."
Here, 'wszystkie' is used as a plural pronoun agreeing with the noun 'książki', signifying the total number of books.
Wszystkie książki na półce są moje.
All the books on the shelf are mine.
Here, 'wszystkie' is used to describe 'dzieci', indicating that every child was involved in the activity.
Wszystkie dzieci bawiły się w ogrodzie.
All the children were playing in the garden.
In this sentence, 'wszystkie' is used to modify 'maile', expressing the entirety of the emails sent.