This is the 149th most frequent Greek word.
όσα
"Όσα" means "as many as" or "whatever" in English, depending on context.
In this sentence, 'όσα' is used to mean 'as many as', referring to the quantity or number of books possessed.
Όσα βιβλία έχω, είναι πάνω στο γραφείο.
As many books as I have, they are on the desk.
Here, 'όσα' is used to mean 'all that', referring to all the knowledge someone has about a certain topic.
Πες μου όσα ξέρεις για το θέμα.
Tell me all that you know about the topic.
In this example, 'όσα' is used for referring to an uncountable quantity, translating as 'as much as' for the amount of money needed.