What Is a Put Option?

定义

A put option is a contract giving the owner the right, but not the obligation, to sell–or sell short–a specified amount of an underlying security at a pre-determined price within a specified time frame. This pre-determined price that buyer of the put option can sell at is called the strike price.

看跌期权是一种合约，赋予所有者权利，但没有义务，在指定时间范围内以预定价格出售或卖空指定数量的基础证券。看跌期权的买方可以出售的这个预定价格称为行使价。

Put options are traded on various underlying assets, including stocks, currencies, bonds, commodities, futures, and indexes. A put option can be contrasted with a call option, which gives the holder the right to buy the underlying at a specified price, either on or before the expiration date of the options contract.

看跌期权交易各种标的资产，包括股票、货币、债券、商品、期货和指数。看跌期权可以与看涨期权形成对比，看涨期权赋予持有人在期权合约到期日或到期日之前以指定价格购买标的物的权利。

KEY TAKEAWAYS

要点

·Put options give holders of the option the right, but not the obligation, to sell a specified amount of an underlying security at a specified price within a specified time frame.

·看跌期权赋予期权持有人在指定时间范围内以指定价格出售指定数量的标的证券的权利，但没有义务。

·Put options are available on a wide range of assets, including stocks, indexes, commodities, and currencies.

·看跌期权适用的资产范围广泛，包括股票、指数、商品和货币。

·Put option prices are impacted by changes in the price of the underlying asset, the option strike price, time decay, interest rates, and volatility.

·看跌期权价格受标的资产价格、期权行使价、时间衰减、利率和波动率变化的影响。

·Put options increase in value as the underlying asset falls in price, as volatility of the underlying asset price increases, and as interest rates decline.

·看跌期权的价值随着标的资产价格下跌、标的资产价格波动性增加以及利率下降而增加。

·They lose value as the underlying asset increases in price, as volatility of the underlying asset price decreases, as interest rates rise, and as the time to expiration nears.

·随着标的资产价格上涨、标的资产价格波动性下降、利率上升以及到期时间临近，看跌期权会失去价值。

How a Put Option Works

看跌期权的运作

A put option becomes more valuable as the price of the underlying stock decreases. Conversely, a put option loses its value as the underlying stock increases. When they are exercised, put options provide a short position in the underlying asset. Because of this, they are typically used for hedging purposes or to speculate on downside price action.

随着标的股票价格的下降，看跌期权变得更有价值。相反，看跌期权会随着标的股票的上涨而失去价值。当看跌期权被行使时，其提供了相关资产的空头头寸。因此，看跌期权通常用于对冲目的或推测下行价格走势。

Investors often use put options in a risk-management strategy known as a protective put. This strategy is used as a form of investment insurance; this strategy is used to ensure that losses in the underlying asset do not exceed a certain amount (namely, the strike price).

投资者经常在称为保护性看跌的风险管理策略中使用看跌期权。该策略被用作一种投资保险，用于确保标的资产的损失不超过一定数额（即行使价）。

In general, the value of a put option decreases as its time to expiration approaches because of the impact of time decay. Time decay accelerates as an option's time to expiration draws closer since there's less time to realize a profit from the trade. When an option loses its time value, the intrinsic value is left over. An option's intrinsic value is equivalent to the difference between the strike price and the underlying stock price. If an option has intrinsic value, it is referred to as in the money (ITM).

一般来说，由于时间衰减的影响，看跌期权的价值会随着到期时间的临近而下降。随着期权的到期时间越来越近，从交易中获利的时间越来越少，时间衰减也会加速。当期权失去其时间价值时，其内在价值剩余。期权的内在价值等于行使价与标的股票价格之间的差额。如果期权具有内在价值，则称为实值 (ITM)。

Out of the money (OTM) and at the money (ATM) put options have no intrinsic value because there is no benefit in exercising the option. Investors have the option of short selling the stock at the current higher market price, rather than exercising an out of the money put option at an undesirable strike price. However, outside of a bear market, short selling is typically riskier than buying options.

虚值 (OTM) 和平值 (ATM) 看跌期权没有内在价值，因为行使期权没有任何好处。投资者可以选择以当前较高的市场价格卖空股票，而不是以不受欢迎的行使价卖出看跌期权。然而，在熊市之外，卖空通常比买入期权风险更大。

Time value, or extrinsic value, is reflected in the premium of the option. If the strike price of a put option is $20, and the underlying is stock is currently trading at $19, there is $1 of intrinsic value in the option. But the put option may trade for $1.35. The extra $0.35 is time value, since the underlying stock price could change before the option expires. Different put options on the same underlying asset may be combined to form put spreads.

时间价值或外在价值反映在期权的溢价中。如果看跌期权的执行价格为 20 美元，而标的股票当前交易价格为 19 美元，则该期权的内在价值为 1 美元。但看跌期权的交易价格可能为 1.35 美元。额外的 0.35 美元是时间价值，因为标的股票价格可能会在期权到期之前发生变化。同一标的资产的不同看跌期权可以组合形成看跌价差。

There are several factors to keep in mind when it comes to selling put options. It's important to understand an option contract's value and profitability when considering a trade, or else you risk the stock falling past the point of profitability.

出售看跌期权时，有几个因素需要牢记。在考虑交易时，了解期权合约的价值和盈利能力非常重要，否则您将面临股票跌破盈利点的风险。

The payoff of a put option at expiration is depicted in the image below:

看跌期权在到期时的收益如下图所示：

Put options, as well as many other types of options, are traded through brokerages. Some brokers have specialized features and benefits for options traders. For those who have an interest in options trading, there are many brokers that specialize in options trading. It's important to identify a broker that is a good match for your investment needs.

看跌期权以及许多其他类型的期权均通过经纪商进行交易。一些经纪人为期权交易者提供专门的功能和好处。对于对期权交易感兴趣的人，有许多专门从事期权交易的经纪人。确定最适合您的投资需求的经纪商很重要。

Alternatives to Exercising a Put Option

行使看跌期权的替代方案

The put option seller, known as the option writer, does not need to hold an option until expiration (and neither does the option buyer). As the underlying stock price moves, the premium of the option will change to reflect the recent underlying price movements. The option buyer can sell their option and, either minimize loss or realize a profit, depending on how the price of the option has changed since they bought it.

看跌期权卖方，称为期权卖方，不需要持有期权直到到期（期权买方也不需要）。随着标的股票价格变动，期权的溢价将发生变化以反映近期标的价格变动。期权买方可以出售他们的期权，并根据期权价格自他们购买以来的变化情况，将损失降至最低或实现利润。

Similarly, the option writer can do the same thing. If the underlying's price is above the strike price, they may do nothing. This is because the option may expire at no value, and this allows them to keep the whole premium. But if the underlying's price is approaching or dropping below the strike price–to avoid a big loss–the option writer may simply buy the option back (which gets them out of the position). The profit or loss is the difference between the premium collected and the premium that is paid in order to get out of the position.

同样，期权卖方亦可以做同样的事情。如果标的价格高于行使价，期权卖方可能什么都不做。因为期权可能会在没有价值的情况下到期，使其可以保留全部溢价。然而，如果标的价格接近或跌破行使价——为避免巨大损失——期权卖方可能会简单地回购期权（以脱离头寸）。盈亏是收取的溢价与为平仓而支付的溢价之间的差额。

Example of a Put Option

示例

Assume an investor owns one put option on the SPDR S&P 500 ETF (SPY)—and assume it is currently trading at $277.00—with a strike price of $260 expiring in one month. For this option, they paid a premium of $0.72, or $72 ($0.72 x 100 shares).

假设投资者拥有 SPDR S&P 500 ETF (SPY) 的一个看跌期权——并假设其目前的交易价格为 277.00 美元——行使价为 260 美元，并将在一个月内到期。对此期权，投资者支付了 0.72 美元或 72 美元（0.72 美元 x 100 股）的溢价。

If shares of SPY fall to $250 and the investor exercises the option, the investor could establish a short sell position in SPY, as if it were initiated from a price of $260 per share. Alternatively, the investor could purchase 100 shares of SPY for $250 in the market and sell the shares to the option's writer for $260 each. Consequently, the investor would make $1,000 (100 x ($260-$250)) on the put option, less the $72 cost they paid for the option. Net profit is $1,000 - $72 = $928, less any commission costs. The maximum loss on the trade is limited to the premium paid, or $72. The maximum profit is attained if SPY falls to $0.

如果 SPY 的股票跌至 250 美元并且投资者行使期权，投资者可以在 SPY 中建立卖空头寸，就好像它是从每股 260 美元的价格开始的。或者，投资者可以在市场上以 250 美元的价格购买 100 股 SPY，然后以每股 260 美元的价格将这些股票出售给期权的卖方。因此，投资者将在看跌期权上赚取 1,000 美元（100 x（260-250 美元）），减去他们为该期权支付的 72 美元成本。净利润为 1,000 美元 - 72 美元 = 928 美元，减去任何佣金成本。交易的最大损失仅限于支付的溢价，即 72 美元。如果 SPY 跌至 0 美元，则获得最大利润。

Contrary to a long put option, a short or written put option obligates an investor to take delivery, or purchase shares, of the underlying stock.

与多头看跌期权相反，空头或卖出看跌期权要求投资者收取或购买标的股票的股份。

Assume an investor is bullish on SPY, which is currently trading at $277, and does not believe it will fall below $260 over the next two months. The investor could collect a premium of $0.72 (x 100 shares) by writing one put option on SPY with a strike price of $260.

假设投资者看好 SPY，目前的交易价格为 277 美元，并且不认为其会在未来两个月内跌破 260 美元。投资者可以通过写一份行使价为 260 美元的 SPY 看跌期权来收取 0.72 美元（x 100 股）的溢价。

The option writer would collect a total of $72 ($0.72 x 100). If SPY stays above the $260 strike price, the investor would keep the premium collected since the options would expire out of the money and be worthless. This is the maximum profit on the trade: $72, or the premium collected.

期权卖方将收取总计 72 美元（0.72 美元 x 100）。如果 SPY 保持在 260 美元的执行价格之上，投资者将保留所收取的溢价，因为期权将到期且毫无价值。交易的最大利润/或收取的溢价：72 美元。

Conversely, if SPY moves below $260, the investor is on the hook for purchasing 100 shares at $260, even if the stock falls to $250, or $200, or lower. No matter how far the stock falls, the put option writer is liable for purchasing shares at $260, meaning they face a theoretical risk of $260 per share, or $26,000 per contract ($260 x 100 shares) if the underlying stock falls to zero.

相反，如果 SPY 跌破 260 美元，即使股票跌至 250 美元或 200 美元或更低，投资者也有可能以 260 美元的价格购买 100 股。无论股票下跌多少，看跌期权卖方均有权以 260 美元的价格购买股票，即如果标的股票跌至零，投资者将面临每股 260 美元的理论风险，或每份合约 26,000 美元（260 美元 x 100 股）的风险。

（英文来源：https://www.investopedia.com/terms/p/putoption.asp）