Call Option
Definition
A call option gives the buyer the right — but not the obligation — to purchase 100 shares of a stock at the strike price any time before expiration. You pay a premium for that right.
Example
“Instead of buying 200 shares, she bought 2 call options with a $50 strike expiring in three weeks for $1.20 each. The stock ran to $54 and her calls were worth $4.10 — a 240% return on the premium.”
Detailed Explanation
Calls give you leveraged, defined-risk exposure to upside movement. The maximum you can lose is the premium you paid — no more. This is the appeal. But that premium is constantly eroding from time decay (theta), and implied volatility changes can dramatically affect the option's price independent of the stock's movement. You can be directionally right on the stock and still lose money on calls if you paid too much for them or held them too long.
The strike price you choose matters more than most new options traders realize. Deep in-the-money calls (strike well below current price) behave more like owning the stock — they're expensive but move nearly dollar-for-dollar. Out-of-the-money calls (strike above current price) are cheaper but require a bigger stock move to profit and decay faster. At-the-money options offer a middle ground. The right choice depends on your time horizon, conviction, and how much leverage you want.
Short-dated calls — especially 0DTE (zero days to expiration) and weekly options — are particularly unforgiving. Theta decay accelerates sharply in the final week before expiration. A stock can move in your direction but still not move fast enough to overcome the time decay. Day traders who use calls need to think carefully about not just direction and magnitude of the move but also timing — all three have to align for a short-dated option trade to work.