American option（美式期权）

An American option, aka an American-style option, is a version of an options contract that allows holders to exercise the option rights at any time before and including the day of expiration.

美式期权是指一种允许期权持有人在到期日之前的任何时间（含到期日当日）行使权利的期权合约。

American options outline the timeframe when the option holder can exercise their option contract rights. These rights allow the holder to buy or sell - depending on if the option is a call or put - the underlying asset, at the set strike price on or before the predetermined expiration date.

美式期权规定了期权持有人行使期权合约权利的大概时间范围，赋予期权持有人在预先确定的到期日之前或当日以既定的执行价格买入或出售标的资产（取决于其是看涨期权还是看跌期权）的权利。

A long call option gives the holder the right to demand delivery of the underlying security or stock on any day within the contract period. This feature includes any day leading up to and the day of expiration. As with all options, the buyer does not have an obligation to receive the shares and is not required to exercise their right. The strike price remains the same specified value throughout the contract.

买入看涨期权赋予持有人在合约期内的任何时间要求交割标的证券或股票的权利，包括到期日之前的任何日期和到日期当日。就所有期权而言，买方没有义务受让股票，也无需行使其权利。执行价格在整个合约期内保持不变。

American put options also allow the execution at any point up to and including the expiration date. This ability gives the buyer the freedom to demand the seller takes delivery of the underlying asset whenever the price falls below the specified strike price.

美式看跌期权同样允许持有人在到期日之前或当日行权，若证券价格低于既定的执行价格，买方有权向卖方出售标的资产。

European option（欧式期权）

An European option is a version of an options contract that limits execution to its expiration date. In other words, if the underlying security such as a stock has moves in price, an investor would not be able to exercise the option early and take delivery of or sell the shares. Instead, the call or put action will only take place on the date of option maturity.

欧式期权是指一种仅能在到期日行权的期权合约。换言之，若标的证券（比如，股票）价格发生波动，投资人不能提早行使期权，买入或卖出股票，只能在期权到期日进行。

European options define the timeframe when holders of an options contract may exercise their contract rights. The rights for the option holder include buying the underlying asset or selling the underlying asset at the specified contract price - the strike price.

欧式期权规定了期权合约持有人行使其合约权利的时间。期权持有人享有的权利包括以既定的合约价格（即执行价格）买入或出售标的资产。

A European call option gives the owner the right to acquire the underlying security at expiry. For an investor to profit from a call option, the stock’s price, at expiry, has to be trading high enough above the strike price to cover the cost of the option premium.

欧式看涨期权赋予持有人在到期日买入标的证券的权利。若希望从看涨期权中获利，到期日的股票交易价格必须高于执行价格，足以支付期权费。

A European put option allows the holder to sell the underlying security at expiry. For an investor to profit from a put option, the stock’s price, at expiry, has to be trading far enough below the strike price strike price to cover the cost of the option premium.

欧式看跌期权赋予持有人在到期日卖出标的证券的权利。若希望从看跌期权中获利，到期日的股票交易价格必须低于执行价格，足以支付期权费。

结论

European options can only be exercised on the expiration date, whereas American options can be exercised at any time between the purchase and expiration dates.

欧式期权仅能在到期日行使，而美式期权可以在购买日期至到期日之间的任何时间行使。

来源：Investopedia