An option is a wasting asset; i.e., it has a limited life, usually nine months. At the end of its life, it either becomes worthless (if it is at-the-money or out-of-the-money), or is automatically exercised for the amount by which it is in-the-money. The CENTER ONLINE Futures Glossary
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The time an options contract lapses. Bloomberg Financial Dictionary
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Corresponds to the expiration date of a contract. The last day on which an option may be exercised into the underlying futures contract. Chicago Mercantile Exchange Glossary
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expiration ex‧pir‧ation [ˌekspˈreɪʆn] noun [uncountable]
when an official document, period of time, or right to buy shares, currency etc expires; = expiry Bre:
• the expiration of the trade agreement
• The first cycle of options have expiry dates in January, April, July, and October.
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expiration UK US /ekspɪˈreɪʃən/ noun [U] US
Financial and business terms. 2012.