Technical Definition

Theta

Theta estimates how an option's value changes as time passes, all else equal.

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Expiration DateOption PremiumCall Option

✦ Key Insight

It explains why a correct directional view can still lose money if the move happens too slowly.

✕ Common Misconceptions

Theta is not constant and can change rapidly near expiration.

Detailed Explanation

Long options commonly lose time value as expiration approaches, while short option positions can benefit from that decay but carry other risks.

In Practice

“A call option loses value over several quiet days even though the underlying price barely changes.”

Dig Deeper

Call Option

A call option gives its holder the right, but not the obligation, to buy an underlying asset at a specified strike price before or at expiration, depending on the contract style.

Put Option

A put option gives its holder the right, but not the obligation, to sell an underlying asset at a specified strike price before or at expiration, depending on contract style.

Expiration Date

An expiration date is the date and time after which an option or expiring derivatives contract is no longer active.

Option Premium

Option premium is the price paid by an option buyer and received by an option seller for the contract.

Implied Volatility (IV)

Implied volatility is the volatility level that an option pricing model backs out from the option's current market price.