call option

exercising a previously agreed upon right to purchase commodities or financial paper

A call option is a financial contract between two parties, the buyer and the seller of this type of option. Often it is simply labeled a "call". The buyer of the option has the right, but not the obligation to buy an agreed quantity of a particular commodity or financial instrument (the underlying instrument) from the seller of the option at a certain time (the expiration date) for a certain price (the strike price). The seller (or "writer") is obligated to sell the commodity or financial instrument should the buyer so decide. The buyer pays a fee (called a premium) for this right.
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An option contract that gives its holder the right (but not the obligation) to purchase a specified number of shares of the underlying stock at the given strike price, on or before the expiration date of the contract.

The right to purchase stock at a specified (exercise) price within a specified time period.