Open interest

Open interest (also known as open contracts or open commitments) denotes the total number of derivative contracts, like futures and options that are currently active on a specific underlying security having specific terms.
Namely, the total contracts for a specific strike price and expiration date, that have been traded, but have not yet expired, have not yet been closed through a closing transaction, or have not yet been terminated via early exercise. A closing transaction occurs when a counter party that longs the contract sells, or, conversely, when a counter party that shorts the contract buys.
Open interest normally serves as an indicator about a security, but it can also be used with other instruments like a currency.