What it means
Theta is the dollar amount an option loses each day from time passage alone. At-the-money options lose theta fastest in the final weeks before expiration. Theta is the cost of being long optionality.
Why it matters
Theta is the bill the long options buyer pays for the right to be wrong without losing more than the premium. Strategy P/L decomposes into vega (vol moves), delta (direction), gamma (acceleration), and theta (time bleed) - managing all four is the job.
How to use it
Calculate the breakeven move per day to overcome theta. If theta is 0.20 on an option with 0.50 delta, you need a 0.40 daily move in the underlying just to break even on time decay.
Take it further
Want a worked example or a deeper dive? Ask Rocky how this concept applies to your specific watchlist or trade idea.
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