you say "meghdar" or "meghdari" when you are talking about amount of something. maybe we can say "meghdar" means "amount", and "meghdari" means "some". for example when you say "meghdari panir" it means "some cheese"

The most straightforward answer that I can give you: Ba'zi= بعضی= Some of Note that in most of the times بعضی is followed by از (az). بعضی از مردم = some of people Even when there is no از the meaning of ba'zi is: some of Meghdar= مقدار = amount Meghdari= مقداری = an amount (of)