Call option
An option giving the right (not the obligation) to buy an instrument at the strike before expiry. The buyer pays a premium; the loss is capped at it.
Definition
A call option gives the buyer the right — not the obligation — to buy the underlying instrument at the strike price before the expiry date. The buyer pays a premium to the seller for that right; the maximum loss on a long call is normally the premium paid.
Example
A GPW-listed stock trades at 100 PLN. You buy a call with a 105 PLN strike expiring in a month and pay a premium of 3 PLN per share. If the price runs to 120 PLN, the option gains value; if it stays below 105 PLN, the call may expire worthless and you lose the premium.
Anti-example / common mistake
A call is not the same as “buying a stock on credit”, and it is not a guarantee that the price will rise. Beginners also confuse a long call (limited loss equal to the premium) with a short call (unlimited risk if the underlying rallies).