A financial contract that gives the buyer the right, but not the obligation, to buy (call) or sell (put) a specified number of foreign currency units to the option seller at a fixed dollar price, up to the optionÃ¢Â€Â™s expiration date. A contract that gives the holder the right to buy (call) or sell (put) a specific amount of a foreign currency at some specified price until a certain (expiration) date. A contract giving the option holder the right to buy or sell an underlying currency at a specified price and on a specified date. The option writer (i.e. seller) holds the obligation to fulfill the other side of the contract.