This is the 113th most frequent Croatian word.
one
The Croatian word "one" means "they" (feminine plural).
In this sentence, 'one' is the feminine plural pronoun for 'they', referring to a group of women.
One su sretne.
They are happy.
Here, 'one' refers to books and serves as a demonstrative adjective specifying which ones to take.
Uzmi one knjige sa stola.
Take those books from the table.
In this case, 'one' functions as a demonstrative pronoun referring to people who assist her.