Why does an option premium change rapidly?

Option premiums move fast because they’re driven by several factors simultaneously, not just the underlying’s price. The underlying asset’s price movement is the most obvious driver, but implied volatility (the market’s expectation of future price swings) can shift premiums significantly even without much movement in the underlying itself, especially ahead of events like earnings or major economic data. Time decay (theta) constantly erodes an option’s extrinsic value as expiry approaches, which accelerates in the final days and hours before expiry regardless of price direction. Options closer to the current market price (at-the-money) tend to be more sensitive to all these factors than deep in- or out-of-the-money contracts. You watch implied volatility and time to expiry alongside the underlying’s price when trying to understand a premium move that seems disproportionate to how much the underlying itself has actually moved.