The set of all the call options or all the put options for a particular stock, index fund, or futures security on a listed exchange. The number of options available for purchase or sale within a given option class will depend on the size and trading volume of the underlying company or index, as well as overall market conditions. An options class can be studied as a gauge of investor sentiment for a given security, as activity in the all of the calls (options to buy) or all of the puts (options to sell) along with premium values signify investors' bets on future price activity. With the advent of LEAPs, these evaluations can go out as far as a year, or more.