Describe 'theta' in options trading and its practical implication for long option positions.

Describe 'theta' in options trading and its practical implication for long option positions.

• A. Theta is the sensitivity of the option price to changes in the underlying price.
• B. Theta is the sensitivity of the option price to changes in implied volatility.
• C. Theta is the rate of change of delta with the underlying.
• D. Theta is the time decay of an option's price; as time passes, option value tends to decrease, all else equal.

Answer: (D)

Theta measures how much an option’s price would change as time passes, holding all else constant. This time passage slowly erodes the value of an option, especially for near-term and at-the-money options, so the decay accelerates as expiration approaches. For a long option holder, this time decay acts as a drag on value. Each day, the option loses some of its time value, even if the underlying price stays the same. To profit, you need the underlying to move in your favor by enough to offset this daily decay, or volatility to rise (which can bolster the option price through vega). Longer-dated options have smaller daily decay, which is why some traders prefer them for this reason. The other ideas describe sensitivity to the underlying price or to volatility, or the change in delta, not the passage of time. Theta is specifically about the time component and its practical impact on a long option position.

Theta measures how much an option’s price would change as time passes, holding all else constant. This time passage slowly erodes the value of an option, especially for near-term and at-the-money options, so the decay accelerates as expiration approaches.

For a long option holder, this time decay acts as a drag on value. Each day, the option loses some of its time value, even if the underlying price stays the same. To profit, you need the underlying to move in your favor by enough to offset this daily decay, or volatility to rise (which can bolster the option price through vega). Longer-dated options have smaller daily decay, which is why some traders prefer them for this reason.

The other ideas describe sensitivity to the underlying price or to volatility, or the change in delta, not the passage of time. Theta is specifically about the time component and its practical impact on a long option position.