A listed option that you can exercise at any point between the day you purchase it and its expiration date is called an American style option. All equity options are American style, no matter where the exchange on which they trade is located.
In contrast, you can exercise European style options only on the last trading day before the expiration date, not before. Index options listed on various US exchanges may be either American- or European-style options.
- Browse Related Terms: American-style option, Base Price, Dealer Sticker Price, European style option, Expiration cycle, Expiration date, Last trading day, Long-term equity anticipation securities (LEAPS), Options class, Options series, Quadruple witching day