An option contract that gives the holder (the buyer) the right, without the obligation, to buy a certain amount of an underlying security from the writer (the seller) of the option, at a specified price (usually known as the strike or exercise price) up to a specified date (the expiration date). The standard amount of underlying security is normally 100 shares. This option is roughly equivalent to an investment in an asset since the holder has the right to purchase that asset in favorable conditions.

A call is also known as an advance guarantee.

Compare: call (finance).