Question: how can you tell the difference between long oo and short oo?
Answer: The letter group ook is mostly pronounced with a short “oo” as in “put” (the only exceptions are “spook” and “snooker”, which are pronounced with a long “oo”). The letter group ood is mostly pronounced with a short "oo", but it can also be pronounced with a long "oo" as in “brood”, “food”, and “mood”.