Expiration Date
The last date on which an option can be exercised; after this date the contract ceases to exist.
The expiration date is the deadline for the option holder to exercise their right. For standard US equity options, expiry falls on the third Friday of the expiration month (or the prior Thursday if Friday is a holiday).
As expiration approaches, time value erodes — a phenomenon captured by theta. Options with shorter time to expiry have less time value, while longer-dated options (LEAPS) carry more.
On expiration, in-the-money options are automatically exercised by the OCC if they are at least $0.01 in the money, unless the holder instructs otherwise.