Open Interest

Open Interest is the total number of active contracts (like options or futures) that haven't been closed or settled yet. Think of it as a headcount of all the open bets in the market at any given moment. You'll see this number quoted alongside options prices, and it matters because high open interest means there's real liquidity—you can actually buy or sell your position without moving the price dramatically. Low open interest can mean you're stuck with a contract nobody wants. For example, if 50,000 call option contracts on TechCorp are still open, that's the open interest; when someone closes their position, that number drops by one.